diff --git a/test/test_dh.c b/test/test_dh.c
index 8cb5889c..11ee1896 100644
--- a/test/test_dh.c
+++ b/test/test_dh.c
@@ -1282,4 +1282,53 @@ int test_dh_x963_kdf(void *data)
 }
 #endif /* HAVE_X963_KDF && WP_HAVE_SHA256 */
 
+/* Pass an oversize OSSL_PARAM (>1024 bytes) for the FFC P component to
+ * EVP_PKEY_fromdata so wp_mp_read_unsigned_bin_le (wp_params.c) hits its
+ * size-guard branch via wp_dh_import_group. Expect failure rather than the
+ * stack buffer overflow that would happen without the guard. */
+int test_dh_fromdata_oversize(void *data)
+{
+    int err = 0;
+    EVP_PKEY_CTX *ctx_wolf = NULL;
+    EVP_PKEY *pkey_wolf = NULL;
+    unsigned char p_oversize[2048];
+    unsigned char g_buf[1] = { 0x02 };
+    OSSL_PARAM params[3];
+    int status;
+
+    (void)data;
+    memset(p_oversize, 0xAA, sizeof(p_oversize));
+
+    PRINT_MSG("Testing EVP_PKEY_fromdata with oversize DH FFC_P component");
+
+    ctx_wolf = EVP_PKEY_CTX_new_from_name(wpLibCtx, "DH", NULL);
+    if (ctx_wolf == NULL) {
+        err = 1;
+    }
+
+    if (err == 0) {
+        err |= EVP_PKEY_fromdata_init(ctx_wolf) != 1;
+    }
+
+    if (err == 0) {
+        params[0] = OSSL_PARAM_construct_BN(OSSL_PKEY_PARAM_FFC_P,
+                                            p_oversize, sizeof(p_oversize));
+        params[1] = OSSL_PARAM_construct_BN(OSSL_PKEY_PARAM_FFC_G,
+                                            g_buf, sizeof(g_buf));
+        params[2] = OSSL_PARAM_construct_end();
+
+        status = EVP_PKEY_fromdata(ctx_wolf, &pkey_wolf,
+                                   EVP_PKEY_KEY_PARAMETERS, params);
+        if (status == 1) {
+            PRINT_MSG("EVP_PKEY_fromdata unexpectedly succeeded with 2048-byte"
+                      " FFC_P");
+            err = 1;
+        }
+        EVP_PKEY_free(pkey_wolf);
+    }
+
+    EVP_PKEY_CTX_free(ctx_wolf);
+    return err;
+}
+
 #endif /* WP_HAVE_DH */
diff --git a/test/test_ecc.c b/test/test_ecc.c
index 800c6a17..2783963b 100644
--- a/test/test_ecc.c
+++ b/test/test_ecc.c
@@ -2791,6 +2791,58 @@ int test_ec_print_public(void* data)
 
     return err;
 }
+
+/* Pass an oversize OSSL_PARAM (>1024 bytes) for the EC private key component
+ * to EVP_PKEY_fromdata so wp_mp_read_unsigned_bin_le (wp_params.c) hits its
+ * size-guard branch via wp_params_get_mp in wp_ecc_import_keypair. Expect
+ * failure rather than the stack buffer overflow that would happen without
+ * the guard. This path also covers ECDH, whose key import shares
+ * wp_ecc_kmgmt. */
+int test_ec_fromdata_oversize(void *data)
+{
+    int err = 0;
+    EVP_PKEY_CTX *ctx_wolf = NULL;
+    EVP_PKEY *pkey_wolf = NULL;
+    unsigned char priv_oversize[2048];
+    char group_name[] = "prime256v1";
+    OSSL_PARAM params[3];
+    int status;
+
+    (void)data;
+    memset(priv_oversize, 0xAA, sizeof(priv_oversize));
+
+    PRINT_MSG("Testing EVP_PKEY_fromdata with oversize EC PRIV_KEY component");
+
+    ctx_wolf = EVP_PKEY_CTX_new_from_name(wpLibCtx, "EC", NULL);
+    if (ctx_wolf == NULL) {
+        err = 1;
+    }
+
+    if (err == 0) {
+        err |= EVP_PKEY_fromdata_init(ctx_wolf) != 1;
+    }
+
+    if (err == 0) {
+        params[0] = OSSL_PARAM_construct_utf8_string(OSSL_PKEY_PARAM_GROUP_NAME,
+                                                     group_name, 0);
+        params[1] = OSSL_PARAM_construct_BN(OSSL_PKEY_PARAM_PRIV_KEY,
+                                            priv_oversize,
+                                            sizeof(priv_oversize));
+        params[2] = OSSL_PARAM_construct_end();
+
+        status = EVP_PKEY_fromdata(ctx_wolf, &pkey_wolf, EVP_PKEY_KEYPAIR,
+                                   params);
+        if (status == 1) {
+            PRINT_MSG("EVP_PKEY_fromdata unexpectedly succeeded with 2048-byte"
+                      " EC PRIV_KEY");
+            err = 1;
+        }
+        EVP_PKEY_free(pkey_wolf);
+    }
+
+    EVP_PKEY_CTX_free(ctx_wolf);
+    return err;
+}
 #endif /* WP_HAVE_EC_P256 */
 
 #endif /* WP_HAVE_ECC */
diff --git a/test/test_rsa.c b/test/test_rsa.c
index 59fd8421..ae7eb59a 100644
--- a/test/test_rsa.c
+++ b/test/test_rsa.c
@@ -1619,6 +1619,55 @@ int test_rsa_fromdata(void* data)
     return err;
 }
 
+/* Pass an oversize OSSL_PARAM (>1024 bytes) for the N component to
+ * EVP_PKEY_fromdata so wp_mp_read_unsigned_bin_le (wp_params.c) hits its
+ * size-guard branch. Expect failure rather than the stack buffer overflow
+ * that would happen without the guard. */
+int test_rsa_fromdata_oversize(void* data)
+{
+    int err = 0;
+    EVP_PKEY_CTX *ctx_wolf = NULL;
+    EVP_PKEY *pkey_wolf = NULL;
+    unsigned char n_oversize[2048];
+    unsigned char e_buf[3] = { 0x01, 0x00, 0x01 };
+    OSSL_PARAM params[3];
+    int status;
+
+    (void)data;
+    memset(n_oversize, 0xAA, sizeof(n_oversize));
+
+    PRINT_MSG("Testing EVP_PKEY_fromdata with oversize RSA n component");
+
+    ctx_wolf = EVP_PKEY_CTX_new_from_name(wpLibCtx, "RSA", NULL);
+    if (ctx_wolf == NULL) {
+        err = 1;
+    }
+
+    if (err == 0) {
+        err |= EVP_PKEY_fromdata_init(ctx_wolf) != 1;
+    }
+
+    if (err == 0) {
+        params[0] = OSSL_PARAM_construct_BN(OSSL_PKEY_PARAM_RSA_N,
+                                            n_oversize, sizeof(n_oversize));
+        params[1] = OSSL_PARAM_construct_BN(OSSL_PKEY_PARAM_RSA_E,
+                                            e_buf, sizeof(e_buf));
+        params[2] = OSSL_PARAM_construct_end();
+
+        status = EVP_PKEY_fromdata(ctx_wolf, &pkey_wolf, EVP_PKEY_PUBLIC_KEY,
+                                   params);
+        if (status == 1) {
+            PRINT_MSG("EVP_PKEY_fromdata unexpectedly succeeded with 2048-byte"
+                      " n");
+            err = 1;
+        }
+        EVP_PKEY_free(pkey_wolf);
+    }
+
+    EVP_PKEY_CTX_free(ctx_wolf);
+    return err;
+}
+
 static int test_rsa_decode_pkcs8_old(void)
 {
     int err = 0;
diff --git a/test/unit.c b/test/unit.c
index 750e3707..3b684d0d 100644
--- a/test/unit.c
+++ b/test/unit.c
@@ -314,6 +314,7 @@ TEST_CASE test_case[] = {
 #if defined(HAVE_X963_KDF) && defined(WP_HAVE_SHA256)
     TEST_DECL(test_dh_x963_kdf, NULL),
 #endif
+    TEST_DECL(test_dh_fromdata_oversize, NULL),
 #ifndef WOLFPROV_QUICKTEST
     TEST_DECL(test_dh_get_params, NULL),
 #endif
@@ -337,6 +338,7 @@ TEST_CASE test_case[] = {
     TEST_DECL(test_rsa_load_key, NULL),
     TEST_DECL(test_rsa_load_cert, NULL),
     TEST_DECL(test_rsa_fromdata, NULL),
+    TEST_DECL(test_rsa_fromdata_oversize, NULL),
     TEST_DECL(test_rsa_decode_pkcs8, NULL),
     TEST_DECL(test_rsa_encode_pkcs8, NULL),
     TEST_DECL(test_rsa_null_init, NULL),
@@ -400,6 +402,7 @@ TEST_CASE test_case[] = {
     TEST_DECL(test_ec_auto_derive_pubkey, NULL),
     TEST_DECL(test_ec_null_init, NULL),
     TEST_DECL(test_ec_print_public, NULL),
+    TEST_DECL(test_ec_fromdata_oversize, NULL),
 #endif
 #ifdef WP_HAVE_EC_P384
     #ifdef WP_HAVE_ECKEYGEN
diff --git a/test/unit.h b/test/unit.h
index b45fcddc..0fd44d04 100644
--- a/test/unit.h
+++ b/test/unit.h
@@ -300,6 +300,7 @@ int test_rsa_pss_restrictions(void *data);
 int test_rsa_load_key(void* data);
 int test_rsa_load_cert(void* data);
 int test_rsa_fromdata(void* data);
+int test_rsa_fromdata_oversize(void* data);
 int test_rsa_decode_pkcs8(void* data);
 int test_rsa_encode_pkcs8(void* data);
 int test_rsa_null_init(void* data);
@@ -320,6 +321,7 @@ int test_dh_pad(void *data);
 #if defined(HAVE_X963_KDF) && defined(WP_HAVE_SHA256)
 int test_dh_x963_kdf(void *data);
 #endif
+int test_dh_fromdata_oversize(void *data);
 #endif /* WP_HAVE_DH */
 
 #ifdef WP_HAVE_ECC
@@ -457,6 +459,7 @@ int test_ec_auto_derive_pubkey(void* data);
 int test_ec_null_init(void* data);
 #ifdef WP_HAVE_EC_P256
 int test_ec_print_public(void* data);
+int test_ec_fromdata_oversize(void* data);
 #endif
 
 #endif /* WP_HAVE_ECC */