chore(deps-major): Update dependency astro to v6 [SECURITY]

[renovate]

ℹ️ Note

This PR body was truncated due to platform limits.

This PR contains the following updates:

Package	Change	Age	Confidence
astro (source)	^2.10.15 → ^6.0.0

---

Atro CSRF Middleware Bypass (security.checkOrigin)

CVE-2024-56140 / GHSA-c4pw-33h3-35xw

More information

Details

Summary

A bug in Astro’s CSRF-protection middleware allows requests to bypass CSRF checks.

Details

When the security.checkOrigin configuration option is set to true, Astro middleware will perform a CSRF check. (Source code: https://github.com/withastro/astro/blob/6031962ab5f56457de986eb82bd24807e926ba1b/packages/astro/src/core/app/middlewares.ts)

For example, with the following Astro configuration:

// astro.config.mjs
import { defineConfig } from 'astro/config';
import node from '@​astrojs/node';

export default defineConfig({
	output: 'server',
	security: { checkOrigin: true },
	adapter: node({ mode: 'standalone' }),
});

A request like the following would be blocked if made from a different origin:

// fetch API or <form action="https://test.example.com/" method="POST">
fetch('https://test.example.com/', {
	method: 'POST',
	credentials: 'include',
	body: 'a=b',
	headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
});
// => Cross-site POST form submissions are forbidden

However, a vulnerability exists that can bypass this security.

Pattern 1: Requests with a semicolon after the Content-Type

A semicolon-delimited parameter is allowed after the type in Content-Type.

Web browsers will treat a Content-Type such as application/x-www-form-urlencoded; abc as a simple request and will not perform preflight validation. In this case, CSRF is not blocked as expected.

fetch('https://test.example.com', {
	method: 'POST',
	credentials: 'include',
	body: 'test',
	headers: { 'Content-Type': 'application/x-www-form-urlencoded; abc' },
});
// => Server-side functions are executed (Response Code 200).

Pattern 2: Request without Content-Type header

The Content-Type header is not required for a request. The following examples are sent without a Content-Type header, resulting in CSRF.

// Pattern 2.1 Request without body
fetch('http://test.example.com', { method: 'POST', credentials: 'include' });

// Pattern 2.2 Blob object without type
fetch('https://test.example.com', {
	method: 'POST',
	credentials: 'include',
	body: new Blob(['a=b'], {}),
});

Impact

Bypass CSRF protection implemented with CSRF middleware.

[!Note]
Even with credentials: 'include', browsers may not send cookies due to third-party cookie blocking. This feature depends on the browser version and settings, and is for privacy protection, not as a CSRF measure.

Severity

• CVSS Score: 5.9 / 10 (Medium)
• Vector String: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:H/A:N

References

• https://github.com/withastro/astro/security/advisories/GHSA-c4pw-33h3-35xw
• https://github.com/withastro/astro/commit/e7d14c374b9d45e27089994a4eb72186d05514de
• https://github.com/withastro/astro/blob/6031962ab5f56457de986eb82bd24807e926ba1b/packages/astro/src/core/app/middlewares.ts
• https://nvd.nist.gov/vuln/detail/CVE-2024-56140
• https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS#simple_requests
• https://github.com/advisories/GHSA-c4pw-33h3-35xw

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro's server source code is exposed to the public if sourcemaps are enabled

CVE-2024-56159 / GHSA-49w6-73cw-chjr

More information

Details

Summary

A bug in the build process allows any unauthenticated user to read parts of the server source code.

Details

During build, along with client assets such as css and font files, the sourcemap files for the server code are moved to a publicly-accessible folder.
https://github.com/withastro/astro/blob/176fe9f113fd912f9b61e848b00bbcfecd6d5c2c/packages/astro/src/core/build/static-build.ts#L139

Any outside party can read them with an unauthorized HTTP GET request to the same server hosting the rest of the website.

While some server files are hashed, making their access obscure, the files corresponding to the file system router (those in src/pages) are predictably named. For example. the sourcemap file for src/pages/index.astro gets named dist/client/pages/index.astro.mjs.map.

PoC

Here is one example of an affected open-source website:
https://creatorsgarten.org/pages/index.astro.mjs.map

The file can be saved and opened using https://evanw.github.io/source-map-visualization/ to reconstruct the source code.

The above accurately mirrors the source code as seen in the repository: https://github.com/creatorsgarten/creatorsgarten.org/blob/main/src/pages/index.astro

The above was found as the 4th result (and the first one on Astro 5.0+) when making the following search query on GitHub.com (search results link):

path:astro.config.mjs @​sentry/astro

This vulnerability is the root cause of https://github.com/withastro/astro/issues/12703, which links to a simple stackblitz project demonstrating the vulnerability. Upon build, notice the contents of the dist/client (referred to as config.build.client in astro code) folder. All astro servers make the folder in question accessible to the public internet without any authentication. It contains .map files corresponding to the code that runs on the server.

Impact

All server-output (SSR) projects on Astro 5 versions v5.0.3 through v5.0.6 (inclusive), that have sourcemaps enabled, either directly or through an add-on such as sentry, are affected. The fix for server-output projects was released in astro@5.0.7.

Additionally, all static-output (SSG) projects built using Astro 4 versions 4.16.17 or older, or Astro 5 versions 5.0.7 or older, that have sourcemaps enabled are also affected. The fix for static-output projects was released in astro@5.0.8, and backported to Astro v4 in astro@4.16.18.

The immediate impact is limited to source code. Any secrets or environment variables are not exposed unless they are present verbatim in the source code.

There is no immediate loss of integrity within the the vulnerable server. However, it is possible to subsequently discover another vulnerability via the revealed source code .

There is no immediate impact to availability of the vulnerable server. However, the presence of an unsafe regular expression, for example, can quickly be exploited to subsequently compromise the availability.

• Network attack vector.
• Low attack complexity.
• No privileges required.
• No interaction required from an authorized user.
• Scope is limited to first party. Although the source code of closed-source third-party software may also be exposed.

Remediation

The fix for server-output projects was released in astro@5.0.7, and the fix for static-output projects was released in astro@5.0.8 and backported to Astro v4 in astro@4.16.18. Users are advised to update immediately if they are using sourcemaps or an integration that enables sourcemaps.

Severity

• CVSS Score: 7.8 / 10 (High)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:H/SI:L/SA:L

References

• https://github.com/withastro/astro/security/advisories/GHSA-49w6-73cw-chjr
• https://github.com/withastro/astro/issues/12703
• https://github.com/withastro/astro/commit/039d022b1bbaacf9ea83071d27affc5318e0e515
• https://github.com/withastro/astro/commit/c879f501ff01b1a3c577de776a1f7100d78f8dd5
• https://github.com/withastro/astro/blob/176fe9f113fd912f9b61e848b00bbcfecd6d5c2c/packages/astro/src/core/build/static-build.ts#L139
• https://nvd.nist.gov/vuln/detail/CVE-2024-56159
• https://github.com/getsentry/sentry-javascript/blob/develop/packages/astro/src/integration/index.ts#L50
• https://github.com/advisories/GHSA-49w6-73cw-chjr

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro allows unauthorized third-party images in _image endpoint

CVE-2025-55303 / GHSA-xf8x-j4p2-f749

More information

Details

Summary

In affected versions of astro, the image optimization endpoint in projects deployed with on-demand rendering allows images from unauthorized third-party domains to be served.

Details

On-demand rendered sites built with Astro include an /_image endpoint which returns optimized versions of images.

The /_image endpoint is restricted to processing local images bundled with the site and also supports remote images from domains the site developer has manually authorized (using the image.domains or image.remotePatterns options).

However, a bug in impacted versions of astro allows an attacker to bypass the third-party domain restrictions by using a protocol-relative URL as the image source, e.g. /_image?href=//example.com/image.png.

Proof of Concept

1. Create a new minimal Astro project (astro@5.13.0).

2. Configure it to use the Node adapter (@astrojs/node@9.1.0 — newer versions are not impacted):

   // astro.config.mjs
   import { defineConfig } from 'astro/config';
   import node from '@​astrojs/node';
   
   export default defineConfig({
   	adapter: node({ mode: 'standalone' }),
   });

3. Build the site by running astro build.

4. Run the server, e.g. with astro preview.

5. Append /_image?href=//placehold.co/600x400 to the preview URL, e.g. http://localhost:4321/_image?href=//placehold.co/600x400

6. The site will serve the image from the unauthorized placehold.co origin.

Impact

Allows a non-authorized third-party to create URLs on an impacted site’s origin that serve unauthorized image content.
In the case of SVG images, this could include the risk of cross-site scripting (XSS) if a user followed a link to a maliciously crafted SVG.

Severity

• CVSS Score: 6.4 / 10 (Medium)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N

References

• https://github.com/withastro/astro/security/advisories/GHSA-xf8x-j4p2-f749
• https://nvd.nist.gov/vuln/detail/CVE-2025-55303
• https://github.com/withastro/astro/commit/4d16de7f95db5d1ec1ce88610d2a95e606e83820
• https://github.com/advisories/GHSA-xf8x-j4p2-f749

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro's X-Forwarded-Host is reflected without validation

CVE-2025-61925 / GHSA-5ff5-9fcw-vg88

More information

Details

Summary

When running Astro in on-demand rendering mode using a adapter such as the node adapter it is possible to maliciously send an X-Forwarded-Host header that is reflected when using the recommended Astro.url property as there is no validation that the value is safe.

Details

Astro reflects the value in X-Forwarded-Host in output when using Astro.url without any validation.

It is common for web servers such as nginx to route requests via the Host header, and forward on other request headers. As such as malicious request can be sent with both a Host header and an X-Forwarded-Host header where the values do not match and the X-Forwarded-Host header is malicious. Astro will then return the malicious value.

This could result in any usages of the Astro.url value in code being manipulated by a request. For example if a user follows guidance and uses Astro.url for a canonical link the canonical link can be manipulated to another site. It is not impossible to imagine that the value could also be used as a login/registration or other form URL as well, resulting in potential redirecting of login credentials to a malicious party.

As this is a per-request attack vector the surface area would only be to the malicious user until one considers that having a caching proxy is a common setup, in which case any page which is cached could persist the malicious value for subsequent users.

Many other frameworks have an allowlist of domains to validate against, or do not have a case where the headers are reflected to avoid such issues.

PoC

• Check out the minimal Astro example found here: https://github.com/Chisnet/minimal_dynamic_astro_server
• nvm use
• yarn run build
• node ./dist/server/entry.mjs
• curl --location 'http://localhost:4321/' --header 'X-Forwarded-Host: www.evil.com' --header 'Host: www.example.com'
• Observe that the response reflects the malicious X-Forwarded-Host header

For the more advanced / dangerous attack vector deploy the application behind a caching proxy, e.g. Cloudflare, set a non-zero cache time, perform the above curl request a few times to establish a cache, then perform the request without the malicious headers and observe that the malicious data is persisted.

Impact

This could affect anyone using Astro in an on-demand/dynamic rendering mode behind a caching proxy.

Severity

• CVSS Score: 6.5 / 10 (Medium)
• Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

References

• https://github.com/withastro/astro/security/advisories/GHSA-5ff5-9fcw-vg88
• https://nvd.nist.gov/vuln/detail/CVE-2025-61925
• https://github.com/withastro/astro/commit/6ee63bfac4856f21b4d4633021b3d2ee059e553f
• https://github.com/Chisnet/minimal_dynamic_astro_server
• https://github.com/advisories/GHSA-5ff5-9fcw-vg88

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro Development Server has Arbitrary Local File Read

CVE-2025-64757 / GHSA-x3h8-62x9-952g

More information

Details

Summary

A vulnerability has been identified in the Astro framework's development server that allows arbitrary local file read access through the image optimization endpoint. The vulnerability affects Astro development environments and allows remote attackers to read any image file accessible to the Node.js process on the host system.

Details

• Title: Arbitrary Local File Read in Astro Development Image Endpoint
• Type: CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
• Component: /packages/astro/src/assets/endpoint/node.ts
• Affected Versions: Astro v5.x development builds (confirmed v5.13.3)
• Attack Vector: Network (HTTP GET request)
• Authentication Required: None

The vulnerability exists in the Node.js image endpoint handler used during development mode. The endpoint accepts an href parameter that specifies the path to an image file. In development mode, this parameter is processed without adequate path validation, allowing attackers to specify absolute file paths.

Vulnerable Code Location: packages/astro/src/assets/endpoint/node.ts

// Vulnerable code in development mode
if (import.meta.env.DEV) {
    fileUrl = pathToFileURL(removeQueryString(replaceFileSystemReferences(src)));
} else {
    // Production has proper path validation
    // ... security checks omitted in dev mode
}

The development branch bypasses the security checks that exist in the production code path, which validates that file paths are within the allowed assets directory.

PoC

Attack Prerequisites

1. Astro development server must be running (astro dev)
2. The /_image endpoint must be accessible to the attacker
3. Target image files must be readable by the Node.js process

Exploit Steps

1. Start Astro Development Server:

   astro dev  # Typically runs on http://localhost:4321

2. Craft Malicious Request:

   GET /_image?href=/[ABSOLUTE_PATH_TO_IMAGE]&w=100&h=100&f=png HTTP/1.1
   Host: localhost:4321

3. Example Attack:

   curl "http://localhost:4321/_image?href=/%2FSystem%2FLibrary%2FImage%20Capture%2FAutomatic%20Tasks%2FMakePDF.app%2FContents%2FResources%2F0blank.jpg&w=100&h=100&f=png" -o stolen.png

Demonstration Results

Test Environment: macOS with Astro v5.13.3

Successful Exploitation:

• Target: /System/Library/Image Capture/Automatic Tasks/MakePDF.app/Contents/Resources/0blank.jpg
• Response: HTTP 200 OK, Content-Type: image/png
• Exfiltration: 303 bytes (100x100 PNG)
• File Created: stolen-image.png containing processed system image

Attack Payload:

http://localhost:4321/_image?href=/%2FSystem%2FLibrary%2FImage%20Capture%2FAutomatic%20Tasks%2FMakePDF.app%2FContents%2FResources%2F0blank.jpg&w=100&h=100&f=png

Server Response:

Status: 200 OK
Content-Type: image/png
Content-Length: 303

Impact

Confidentiality Impact: HIGH

• Scope: Any image file readable by the Node.js process
• Exfiltration Method: Complete file contents via HTTP response (transformed to PNG)

Integrity Impact: NONE

• The vulnerability only allows reading files, not modification

Availability Impact: NONE

• No direct impact on system availability
• Potential for resource exhaustion through repeated large image requests

Affected Components

Primary Component

• File: packages/astro/src/assets/endpoint/node.ts
• Function: loadLocalImage()
• Lines: Development mode branch (~25-35)

Secondary Components

• File: packages/astro/src/assets/endpoint/generic.ts
• Impact: Uses different code path, not directly vulnerable
• Note: Implements proper remote allowlist validation

Severity

• CVSS Score: 3.5 / 10 (Low)
• Vector String: CVSS:3.1/AV:A/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

References

• https://github.com/withastro/astro/security/advisories/GHSA-x3h8-62x9-952g
• https://nvd.nist.gov/vuln/detail/CVE-2025-64757
• https://github.com/withastro/astro/commit/b8ca69b97149becefaf89bf21853de9c905cdbb7
• https://github.com/advisories/GHSA-x3h8-62x9-952g

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro vulnerable to reflected XSS via the server islands feature

CVE-2025-64764 / GHSA-wrwg-2hg8-v723

More information

Details

Summary

After some research it appears that it is possible to obtain a reflected XSS when the server islands feature is used in the targeted application, regardless of what was intended by the component template(s).

Details

Server islands run in their own isolated context outside of the page request and use the following pattern path to hydrate the page: /_server-islands/[name]. These paths can be called via GET or POST and use three parameters:

• e: component to export
• p: the transmitted properties, encrypted
• s: for the slots

Slots are placeholders for external HTML content, and therefore allow, by default, the injection of code if the component template supports it, nothing exceptional in principle, just a feature.

This is where it becomes problematic: it is possible, independently of the component template used, even if it is completely empty, to inject a slot containing an XSS payload, whose parent is a tag whose name is is the absolute path of the island file. Enabling reflected XSS on any application, regardless of the component templates used, provided that the server islands is used at least once.

How ?

By default, when a call is made to the endpoint /_server-islands/[name], the value of the parameter e is default, pointing to a function exported by the component's module.

Upon further investigation, we find that two other values ​​are possible for the component export (param e) in a typical configuration: url and file. file returns a string value corresponding to the absolute path of the island file. Since the value is of type string, it fulfills the following condition and leads to this code block:

An entire template is created, completely independently, and then returned:

• the absolute path name is sanitized and then injected as the tag name
• childSlots, the value provided to the s parameter, is injected as a child

All of this is done using markHTMLString. This allows the injection of any XSS payload, even if the component template intended by the application is initially empty or does not provide for the use of slots.

Proof of concept

For our Proof of Concept (PoC), we will use a minimal repository:

• Latest Astro version at the time (5.15.6)
• Use of Island servers, with a completely empty component, to demonstrate what we explained previously

Download the PoC repository

Access the following URL and note the opening of the popup, demonstrating the reflected XSS:

http://localhost:4321/_server-islands/ServerTime?e=file&p=&s={%22zhero%22:%22%3Cimg%20src=x%20onerror=alert(0)%3E%22}

The value of the parameter s must be in JSON format and the payload must be injected at the value level, not the key level :

Despite the initial template being empty, it is created because the value of the URL parameter e is set to file, as explained earlier. The parent tag is the name of the component's internal route, and its child is the value of the key "zhero" (the name doesn't matter) of the URL parameter s.

Credits

• Allam Rachid (zhero;)
• Allam Yasser (inzo)

Severity

• CVSS Score: 7.1 / 10 (High)
• Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:N

References

• https://github.com/withastro/astro/security/advisories/GHSA-wrwg-2hg8-v723
• https://nvd.nist.gov/vuln/detail/CVE-2025-64764
• https://github.com/withastro/astro/commit/790d9425f39bbbb462f1c27615781cd965009f91
• https://github.com/advisories/GHSA-wrwg-2hg8-v723

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro's middleware authentication checks based on url.pathname can be bypassed via url encoded values

CVE-2025-64765 / GHSA-ggxq-hp9w-j794

More information

Details

A mismatch exists between how Astro normalizes request paths for routing/rendering and how the application’s middleware reads the path for validation checks. Astro internally applies decodeURI() to determine which route to render, while the middleware uses context.url.pathname without applying the same normalization (decodeURI).

This discrepancy may allow attackers to reach protected routes (e.g., /admin) using encoded path variants that pass routing but bypass validation checks.

https://github.com/withastro/astro/blob/ebc4b1cde82c76076d5d673b5b70f94be2c066f3/packages/astro/src/vite-plugin-astro-server/request.ts#L40-L44

/** The main logic to route dev server requests to pages in Astro. */
export async function handleRequest({
    pipeline,
    routesList,
    controller,
    incomingRequest,
    incomingResponse,
}: HandleRequest) {
    const { config, loader } = pipeline;
    const origin = `${loader.isHttps() ? 'https' : 'http'}://${
        incomingRequest.headers[':authority'] ?? incomingRequest.headers.host
    }`;

    const url = new URL(origin + incomingRequest.url);
    let pathname: string;
    if (config.trailingSlash === 'never' && !incomingRequest.url) {
        pathname = '';
    } else {
        // We already have a middleware that checks if there's an incoming URL that has invalid URI, so it's safe
        // to not handle the error: packages/astro/src/vite-plugin-astro-server/base.ts
        pathname = decodeURI(url.pathname); // here this url is for routing/rendering
    }

    // Add config.base back to url before passing it to SSR
    url.pathname = removeTrailingForwardSlash(config.base) + url.pathname; // this is used for middleware context

Consider an application having the following middleware code:

import { defineMiddleware } from "astro/middleware";

export const onRequest = defineMiddleware(async (context, next) => {
  const isAuthed = false;  // simulate no auth
  if (context.url.pathname === "/admin" && !isAuthed) {
    return context.redirect("/");
  }
  return next();
});

context.url.pathname is validated , if it's equal to /admin the isAuthed property must be true for the next() method to be called. The same example can be found in the official docs https://docs.astro.build/en/guides/authentication/

context.url.pathname returns the raw version which is /%61admin while pathname which is used for routing/rendering /admin, this creates a path normalization mismatch.

By sending the following request, it's possible to bypass the middleware check

GET /%61dmin HTTP/1.1
Host: localhost:3000

Remediation

Ensure middleware context has the same normalized pathname value that Astro uses internally, because any difference could allow it to bypass such checks. In short maybe something like this

        pathname = decodeURI(url.pathname);
    }

    // Add config.base back to url before passing it to SSR
-    url.pathname = removeTrailingForwardSlash(config.base) + url.pathname;
+    url.pathname = removeTrailingForwardSlash(config.base) + decodeURI(url.pathname);

Thank you, let @​Sudistark know if any more info is needed. Happy to help :)

Severity

• CVSS Score: 6.9 / 10 (Medium)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

References

• https://github.com/withastro/astro/security/advisories/GHSA-ggxq-hp9w-j794
• https://nvd.nist.gov/vuln/detail/CVE-2025-64765
• https://github.com/withastro/astro/commit/6f800813516b07bbe12c666a92937525fddb58ce
• https://github.com/advisories/GHSA-ggxq-hp9w-j794

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro Cloudflare adapter has Stored Cross-site Scripting vulnerability in /_image endpoint

CVE-2025-65019 / GHSA-fvmw-cj7j-j39q

More information

Details

Summary
A Cross-Site Scripting (XSS) vulnerability exists in Astro when using the @​astrojs/cloudflare adapter with output: 'server'. The built-in image optimization endpoint (/_image) uses isRemoteAllowed() from Astro’s internal helpers, which unconditionally allows data: URLs. When the endpoint receives a valid data: URL pointing to a malicious SVG containing JavaScript, and the Cloudflare-specific implementation performs a 302 redirect back to the original data: URL, the browser directly executes the embedded JavaScript. This completely bypasses any domain allow-listing (image.domains / image.remotePatterns) and typical Content Security Policy mitigations.

Affected Versions

• @astrojs/cloudflare ≤ 12.6.10 (and likely all previous versions)
• Astro ≥ 4.x when used with output: 'server' and the Cloudflare adapter

Root Cause – Vulnerable Code
File: node_modules/@​astrojs/internal-helpers/src/remote.ts

export function isRemoteAllowed(src: string, ...): boolean {
  if (!URL.canParse(src)) {
    return false;
  }
  const url = new URL(src);

  // Data URLs are always allowed 
  if (url.protocol === 'data:') {
    return true;
  }

  // Non-http(s) protocols are never allowed
  if (!['http:', 'https:'].includes(url.protocol)) {
    return false;
  }
  // ... further http/https allow-list checks
}

In the Cloudflare adapter, the /_image endpoint contains logic similar to:

	const href = ctx.url.searchParams.get('href');
	if (!href) {
		// return error 
	}

	if (isRemotePath(href)) {
		if (isRemoteAllowed(href, imageConfig) === false) {
			// return error
		} else {
            //redirect to return the image 
			return Response.redirect(href, 302);
		}
	}

Because data: URLs are considered “allowed”, a request such as:
https://example.com/_image?href=data:image/svg+xml;base64,PHN2Zy... (base64-encoded malicious SVG)

triggers a 302 redirect directly to the data: URL, causing the browser to render and execute the malicious JavaScript inside the SVG.

Proof of Concept (PoC)

1. Create a minimal Astro project with Cloudflare adapter (output: 'server').
2. Deploy to Cloudflare Pages or Workers.
3. Request the image endpoint with the following payload:

https://yoursite.com/_image?href=data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjxzY3JpcHQ+YWxlcnQoJ3pvbWFzZWMnKTwvc2NyaXB0Pjwvc3ZnPg==

(Base64 decodes to: <svg xmlns="http://www.w3.org/2000/svg"><script>alert('zomasec')</script></svg>)

4. The endpoint returns a 302 redirect to the data: URL → browser executes the <script> → alert() fires.

Impact

• Reflected/Strored XSS (depending on application usage)
• Session hijacking (access to cookies, localStorage, etc.)
• Account takeover when combined with CSRF
• Data exfiltration to attacker-controlled servers
• Bypasses image.domains / image.remotePatterns configuration entirely

Safe vs Vulnerable Behavior
Other Astro adapters (Node, Vercel, etc.) typically proxy and rasterize SVGs, stripping JavaScript. The Cloudflare adapter currently redirects to remote resources (including data: URLs), making it uniquely vulnerable.

References

• Vulnerable function: https://github.com/withastro/astro/blob/main/packages/internal-helpers/src/remote.ts
• Similar data: URL bypass in WordPress: CVE-2025-2575

Severity

• CVSS Score: 5.4 / 10 (Medium)
• Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

References

• https://github.com/withastro/astro/security/advisories/GHSA-fvmw-cj7j-j39q
• https://nvd.nist.gov/vuln/detail/CVE-2025-65019
• https://github.com/withastro/astro/commit/9e9c528191b6f5e06db9daf6ad26b8f68016e533
• https://github.com/advisories/GHSA-fvmw-cj7j-j39q

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro has an Authentication Bypass via Double URL Encoding, a bypass for CVE-2025-64765

CVE-2025-66202 / GHSA-whqg-ppgf-wp8c

More information

Details

Authentication Bypass via Double URL Encoding in Astro

Bypass for CVE-2025-64765 / GHSA-ggxq-hp9w-j794

---

Summary

A double URL encoding bypass allows any unauthenticated attacker to bypass path-based authentication checks in Astro middleware, granting unauthorized access to protected routes. While the original CVE-2025-64765 (single URL encoding) was fixed in v5.15.8, the fix is insufficient as it only decodes once. By using double-encoded URLs like /%2561dmin instead of /%61dmin, attackers can still bypass authentication and access protected resources such as /admin, /api/internal, or any route protected by middleware pathname checks.

Fix

A more secure fix is just decoding once, then if the request has a %xx format, return a 400 error by using something like :

if (containsEncodedCharacters(pathname)) {
            // Multi-level encoding detected - reject request
            return new Response(
                'Bad Request: Multi-level URL encoding is not allowed',
                {
                    status: 400,
                    headers: { 'Content-Type': 'text/plain' }
                }
            );
        }

Severity

• CVSS Score: 6.5 / 10 (Medium)
• Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

References

• https://github.com/withastro/astro/security/advisories/GHSA-ggxq-hp9w-j794
• https://github.com/withastro/astro/security/advisories/GHSA-whqg-ppgf-wp8c
• https://nvd.nist.gov/vuln/detail/CVE-2025-64765
• https://github.com/withastro/astro/commit/6f800813516b07bbe12c666a92937525fddb58ce
• https://nvd.nist.gov/vuln/detail/CVE-2025-66202
• https://github.com/advisories/GHSA-whqg-ppgf-wp8c

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro: Remote allowlist bypass via unanchored matchPathname wildcard

CVE-2026-33769 / GHSA-g735-7g2w-hh3f

More information

Details

Summary

This issue concerns Astro's remotePatterns path enforcement for remote URLs used by server-side fetchers such as the image optimization endpoint. The path matching logic for /* wildcards is unanchored, so a pathname that contains the allowed prefix later in the path can still match. As a result, an attacker can fetch paths outside the intended allowlisted prefix on an otherwise allowed host. In our PoC, both the allowed path and a bypass path returned 200 with the same SVG payload, confirming the bypass.

Impact

Attackers can fetch unintended remote resources on an allowlisted host via the image endpoint, expanding SSRF/data exposure beyond the configured path prefix.

Description

Taint flow: request -> transform.src -> isRemoteAllowed() -> matchPattern() -> matchPathname()

User-controlled href is parsed into transform.src and validated via isRemoteAllowed():

Source: https://github.com/withastro/astro/blob/e0f1a2b3e4bc908bd5e148c698efb6f41a42c8ea/packages/astro/src/assets/endpoint/generic.ts#L43-L56

const url = new URL(request.url);
const transform = await imageService.parseURL(url, imageConfig);

const isRemoteImage = isRemotePath(transform.src);

if (isRemoteImage && isRemoteAllowed(transform.src, imageConfig) === false) {
  return new Response('Forbidden', { status: 403 });
}

isRemoteAllowed() checks each remotePattern via matchPattern():

Source: https://github.com/withastro/astro/blob/e0f1a2b3e4bc908bd5e148c698efb6f41a42c8ea/packages/internal-helpers/src/remote.ts#L15-L21

export function matchPattern(url: URL, remotePattern: RemotePattern): boolean {
  return (
    matchProtocol(url, remotePattern.protocol) &&
    matchHostname(url, remotePattern.hostname, true) &&
    matchPort(url, remotePattern.port) &&
    matchPathname(url, remotePattern.pathname, true)
  );
}

The vulnerable logic in matchPathname() uses replace() without anchoring the prefix for /* patterns:

Source: https://github.com/withastro/astro/blob/e0f1a2b3e4bc908bd5e148c698efb6f41a42c8ea/packages/internal-helpers/src/remote.ts#L85-L99

} else if (pathname.endsWith('/*')) {
  const slicedPathname = pathname.slice(0, -1); // * length
  const additionalPathChunks = url.pathname
    .replace(slicedPathname, '')
    .split('/')
    .filter(Boolean);
  return additionalPathChunks.length === 1;
}

Vulnerable code flow:

1. isRemoteAllowed() evaluates remotePatterns for a requested URL.
2. matchPathname() handles pathname: "/img/*" using .replace() on the URL path.
3. A path such as /evil/img/secret incorrectly matches because /img/ is removed even when it's not at the start.
4. The image endpoint fetches and returns the remote resource.

PoC

The PoC starts a local attacker server and configures remotePatterns to allow only /img/*. It then requests the image endpoint with two URLs: an allowed path and a bypass path with /img/ in the middle. Both requests returned the SVG payload, showing the path restriction was bypassed.

Vulnerable config

import { defineConfig } from 'astro/config';
import node from '@​astrojs/node';

export default defineConfig({
  output: 'server',
  adapter: node({ mode: 'standalone' }),
  image: {
    remotePatterns: [
      { protocol: 'https', hostname: 'cdn.example', pathname: '/img/*' },
      { protocol: 'http', hostname: '127.0.0.1', port: '9999', pathname: '/img/*' },
    ],
  },
});

Affected pages

This PoC targets the /_image endpoint directly; no additional pages are required.

PoC Code

import http.client
import json
import urllib.parse

HOST = "127.0.0.1"
PORT = 4321

def fetch(path: str) -> dict:
    conn = http.client.HTTPConnection(HOST, PORT, timeout=10)
    conn.request("GET", path, headers={"Host": f"{HOST}:{PORT}"})
    resp = conn.getresponse()
    body = resp.read(2000).decode("utf-8", errors="replace")
    conn.close()
    return {
        "path": path,
        "status": resp.status,
        "reason": resp.reason,
        "headers": dict(resp.getheaders()),
        "body_snippet": body[:400],
    }

allowed = urllib.parse.quote("http://127.0.0.1:9999/img/allowed.svg", safe="")
bypass = urllib.parse.quote("http://127.0.0.1:9999/evil/img/secret.svg", safe="")

##### Both pass, second should fail

results = {
    "allowed": fetch(f"/_image?href={allowed}&f=svg"),
    "bypass": fetch(f"/_image?href={bypass}&f=svg"),
}

print(json.dumps(results, indent=2))

Attacker server

from http.server import BaseHTTPRequestHandler, HTTPServer

HOST = "127.0.0.1"
PORT = 9999

PAYLOAD = """<svg xmlns=\"http://www.w3.org/2000/svg\">
  <text>OK</text>
</svg>
"""

class Handler(BaseHTTPRequestHandler):
    def do_GET(self):
        print(f">>> {self.command} {self.path}")
        if self.path.endswith(".svg") or "/img/" in self.path:
            self.send_response(200)
            self.send_header("Content-Type", "image/svg+xml")
            self.send_header("Cache-Control", "no-store")
            self.end_headers()
            self.wfile.write(PAYLOAD.encode("utf-8"))
            return

        self.send_response(200)
        self.send_header("Content-Type", "text/plain")
        self.end_headers()
        self.wfile.write(b"ok")

    def log_message(self, format, *args):
        return

if __name__ == "__main__":
    server = HTTPServer((HOST, PORT), Handler)
    print(f"HTTP logger listening on http://{HOST}:{PORT}")
    server.serve_forever()

PoC Steps

1. Bootstrap default Astro project.
2. Add the vulnerable config and attacker server.
3. Build the project.
4. Start the attacker server.
5. Start the Astro server.
6. Run the PoC.
7. Observe the console output showing both the allowed and bypass requests returning the SVG payload.

Severity

• CVSS Score: 2.9 / 10 (Low)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P

References

• https://github.com/withastro/astro/security/advisories/GHSA-g735-7g2w-hh3f
• https://nvd.nist.gov/vuln/detail/CVE-2026-33769
• https://github.com/advisories/GHSA-g735-7g2w-hh3f

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro: XSS in define:vars via incomplete </script> tag sanitization

CVE-2026-41067 / GHSA-j687-52p2-xcff

More information

Details

Summary

The defineScriptVars function in Astro's server-side rendering pipeline uses a case-sensitive regex /<\/script>/g to sanitize values injected into inline <script> tags via the define:vars directive. HTML parsers close <script> elements case-insensitively and also accept whitespace or / before the closing >, allowing an attacker to bypass the sanitization with payloads like </Script>, </script >, or </script/> and inject arbitrary HTML/JavaScript.

Details

The vulnerable function is defineScriptVars at packages/astro/src/runtime/server/render/util.ts:42-53:

export function defineScriptVars(vars: Record<any, any>) {
	let output = '';
	for (const [key, value] of Object.entries(vars)) {
		output += `const ${toIdent(key)} = ${JSON.stringify(value)?.replace(
			/<\/script>/g,       // ← Case-sensitive, exact match only
			'\\x3C/script>',
		)};\n`;
	}
	return markHTMLString(output);
}

This function is called from renderElement at util.ts:172-174 when a <script> element has define:vars:

if (name === 'script') {
	delete props.hoist;
	children = defineScriptVars(defineVars) + '\n' + children;
}

The regex /<\/script>/g fails to match three classes of closing script tags that HTML parsers accept per the HTML specification §13.2.6.4:

1. Case variations: </Script>, </SCRIPT>, </sCrIpT> — HTML tag names are case-insensitive but the regex has no i flag.
2. Whitespace before >: </script >, </script\t>, </script\n> — after the tag name, the HTML tokenizer enters the "before attribute name" state on ASCII whitespace.
3. Self-closing slash: </script/> — the tokenizer enters "self-closing start tag" state on /.

JSON.stringify() does not escape <, >, or / characters, so all these payloads pass through serialization unchanged.

Execution flow: User-controlled input (e.g., Astro.url.searchParams) → assigned to a variable → passed via define:vars on a <script> tag → renderElement → defineScriptVars → incomplete sanitization → injected into <script> block in HTML response → browser closes the script element early → attacker-controlled HTML parsed and executed.

PoC

Step 1: Create an SSR Astro page (src/pages/index.astro):

---
const name = Astro.url.searchParams.get('name') || 'World';
---
<html>
<body>
  <h1>Hello</h1>
  <script define:vars=>
    console.log(name);
  </script>
</body>
</html>

Step 2: Ensure SSR is enabled in astro.config.mjs:

export default defineConfig({
  output: 'server'
});

Step 3: Start the dev server and visit:

http://localhost:4321/?name=</Script><img/src=x%20onerror=alert(document.cookie)>

Step 4: View the HTML source. The output contains:

<script>const name = "</Script><img/src=x onerror=alert(document.cookie)>";
  console.log(name);
</script>

The browser's HTML parser matches </Script> case-insensitively, closing the script block. The <img onerror=alert(document.cookie)> is then parsed as HTML and the JavaScript in onerror executes.

Alternative bypass payloads:

/?name=</script ><img/src=x onerror=alert(1)>
/?name=</script/><img/src=x onerror=alert(1)>
/?name=</SCRIPT><img/src=x onerror=alert(1)>

Impact

An attacker can execute arbitrary JavaScript in the context of a victim's browser session on any SSR Astro application that passes request-derived data to define:vars on a <script> tag. This is a documented and expected usage pattern in Astro.

Exploitation enables:

• Session hijacking via cookie theft (document.cookie)
• Credential theft by injecting fake login forms or keyloggers
• Defacement of the rendered page
• Redirection to attacker-controlled domains

The vulnerability affects all Astro versions that support define:vars and is exploitable in any SSR deployment where user input reaches a define:vars script variable.

Recommended Fix

Replace the case-sensitive exact-match regex with a comprehensive escape that covers all HTML parser edge cases. The simplest correct fix is to escape all < characters in the JSON output:

export function defineScriptVars(vars: Record<any, any>) {
	let output = '';
	for (const [key, value] of Object.entries(vars)) {
		output += `const ${toIdent(key)} = ${JSON.stringify(value)?.replace(
			/</g,
			'\\u003c',
		)};\n`;
	}
	return markHTMLString(output);
}

This is the standard approach used by frameworks like Next.js and Rails. Replacing every < with \u003c is safe inside JSON string contexts (JavaScript treats \u003c as < at runtime) and eliminates all possible </script> variants including case variations, whitespace, and self-closing forms.

Severity

• CVSS Score: 6.1 / 10 (Medium)
• Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

References

• https://github.com/withastro/astro/security/advisories/GHSA-j687-52p2-xcff
• https://github.com/withastro/astro/releases/tag/astro@6.1.6
• https://nvd.nist.gov/vuln/detail/CVE-2026-41067
• https://github.com/advisories/GHSA-j687-52p2-xcff

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro: Server island encrypted parameters vulnerable to cross-component replay

CVE-2026-45028 / GHSA-xr5h-phrj-8vxv

More information

Details

Impact

Astro versions prior to 6.1.10 used AES-GCM encryption to protect the confidentiality and integrity of server island props and slots parameters, but did not bind the ciphertext to its intended component or parameter type. An attacker could replay one component's encrypted props (p) value as another component's slots (s) value, or vice versa.

Since slots contain raw unescaped HTML while props may contain user-controlled values, this could lead to XSS in applications that meet all of the following conditions:

• The application uses server islands
• Two different server island components share the same key name for a prop and a slot
• An attacker has full control over the value of the overlapping prop (requires a dynamically rendered page)

These conditions are very unlikely to occur in real-world production applications.

Patches

This has been patched in astro@6.1.10.

The fix binds each encrypted parameter to its target component and purpose using AES-GCM authenticated additional data (AAD). Each ciphertext now includes context like props:IslandName or slots:IslandName, so encrypted data for one component cannot be replayed against a different component, and encrypted props cannot be reused as slots.

References

• Fix PR: https://github.com/withastro/astro/pull/16457
• Example demonstrating the vulnerability: https://github.com/CyberSecurityAustria/ACSC2026-web-astronomical

Severity

• CVSS Score: 2.9 / 10 (Low)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P

References

• https://github.com/withastro/astro/security/advisories/GHSA-xr5h-phrj-8vxv
• https://github.com/withastro/astro/pull/16457
• https://github.com/withastro/astro/commit/3d82220a1549e699e34ed433f3846a919f4c02bd
• https://nvd.nist.gov/vuln/detail/CVE-2026-45028
• https://github.com/advisories/GHSA-xr5h-phrj-8vxv

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro: Reflected XSS via unescaped slot name

CVE-2026-50146 / GHSA-8hv8-536x-4wqp

More information

Details

Summary

When a component uses a client:* directive, Astro inserts named slot content into a data-astro-template attribute without HTML escaping the slot name allowing an attacker to break out of the attribute context and inject arbitrary HTML, resulting in reflected XSS during SSR.

This is similar to GHSA-wrwg-2hg8-v723 but exploits a different injection point.

Vulnerable Code

packages/astro/src/runtime/server/render/component.ts:371:376

// component.ts:371
`<template data-astro-template${key !== 'default' ? `="${key}"` : ''}>${children[key]}</template>`

I found that key is interpolated directly into the attribute value without proper escaping.

Proof of Concept

For the PoC, I set up with a minimal repository with Astro 6.3.1, Node.js: v26.0.0.

astro.config.mjs

import react from '@​astrojs/react';
import node from '@​astrojs/node';
import { defineConfig } from 'astro/config';
export default defineConfig({
  output: 'server',
  adapter: node({ mode: 'standalone' }),
  integrations: [react()],
});

src/pages/index.astro

---
import Wrapper from '../components/Wrapper.jsx';
const slotName = Astro.url.searchParams.get('tab') ?? 'default';
---
<html><body>
  <Wrapper client:load>
    <div slot={slotName}>content</div>
  </Wrapper>
</body></html>

src/components/Wrapper.jsx

export default function Wrapper() { return null; }

Payload:

abc"></template></astro-island><img src=x onerror=confirm(document.domain)><!--

Accessing this URL will trigger the popup.

http://localhost:4321/?tab=abc%22%3E%3C%2Ftemplate%3E%3C%2Fastro-island%3E%3Cimg+src%3Dx+onerror%3Dconfirm(document.domain)%3E%3C!--

This will render in html.

<template data-astro-template="abc"></template></astro-island>
<img src=x onerror=confirm(document.domain)><!--">content</template>

Fix

I suggest leveraging the existing escape function on the slot name.

// component.ts:371
`<template data-astro-template${key !== 'default' ? `="${escapeHTML(String(key))}"` : ''}>${children[key]}</temp

> ✂ **Note**
> 
> PR body was truncated to here.