diff --git a/src/wp_dec_pem2der.c b/src/wp_dec_pem2der.c
index 55a84846..0635db05 100644
--- a/src/wp_dec_pem2der.c
+++ b/src/wp_dec_pem2der.c
@@ -439,8 +439,8 @@ static int wp_pem2der_decode(wp_Pem2Der* ctx, OSSL_CORE_BIO* coreBio,
                 dataCbArg, pwCb, pwCbArg);
         }
     }
-    /* Dispose of the PEM data buffer. */
-    OPENSSL_free(data);
+    /* Dispose of the PEM data buffer (may contain private key material). */
+    OPENSSL_clear_free(data, len);
 
     WOLFPROV_LEAVE(WP_LOG_COMP_PK, __FILE__ ":" WOLFPROV_STRINGIZE(__LINE__), ok);
     return ok;
diff --git a/src/wp_ecx_kmgmt.c b/src/wp_ecx_kmgmt.c
index 2a80b977..d3a60b44 100644
--- a/src/wp_ecx_kmgmt.c
+++ b/src/wp_ecx_kmgmt.c
@@ -339,6 +339,8 @@ void wp_ecx_free(wp_Ecx* ecx)
             wc_FreeMutex(&ecx->mutex);
     #endif
             (*ecx->data->freeKey)((void*)&ecx->key);
+            /* unclamped holds 2 bytes of the original private key. */
+            OPENSSL_cleanse(ecx->unclamped, sizeof(ecx->unclamped));
             OPENSSL_free(ecx);
         }
     }
diff --git a/src/wp_file_store.c b/src/wp_file_store.c
index 571b180d..eebd8d11 100644
--- a/src/wp_file_store.c
+++ b/src/wp_file_store.c
@@ -440,6 +440,9 @@ static void wp_bio_consume_all(BIO* bio)
     do {
         bytes_read = BIO_read(bio, buffer, sizeof(buffer));
     } while (bytes_read > 0);
+
+    /* buffer may hold private key material from the drained file. */
+    OPENSSL_cleanse(buffer, sizeof(buffer));
 }
 
 /**
diff --git a/src/wp_hkdf.c b/src/wp_hkdf.c
index 6dabe2f5..43a53d5e 100644
--- a/src/wp_hkdf.c
+++ b/src/wp_hkdf.c
@@ -674,6 +674,9 @@ static int wp_tls13_hkdf_extract(wp_HkdfCtx* ctx, unsigned char* key,
         }
     }
 
+    /* secret may hold a Derive-Secret intermediate used as the salt. */
+    OPENSSL_cleanse(secret, sizeof(secret));
+
     WOLFPROV_LEAVE(WP_LOG_COMP_HKDF, __FILE__ ":" WOLFPROV_STRINGIZE(__LINE__), ok);
     return ok;
 }
diff --git a/src/wp_internal.c b/src/wp_internal.c
index 058e71f0..ceb2fce6 100644
--- a/src/wp_internal.c
+++ b/src/wp_internal.c
@@ -1207,6 +1207,9 @@ int wp_read_der_bio(WOLFPROV_CTX *provctx, OSSL_CORE_BIO *coreBio, unsigned char
         }
     }
 
+    /* buf may hold plaintext private key DER fragments. */
+    OPENSSL_cleanse(buf, sizeof(buf));
+
     BIO_free(bio);
     WOLFPROV_LEAVE(WP_LOG_COMP_PROVIDER, __FILE__ ":" WOLFPROV_STRINGIZE(__LINE__), ok);
     return ok;
@@ -1266,6 +1269,9 @@ int wp_read_pem_bio(WOLFPROV_CTX *provctx, OSSL_CORE_BIO *coreBio,
         }
     }
 
+    /* buf may hold plaintext private key PEM line fragments. */
+    OPENSSL_cleanse(buf, sizeof(buf));
+
     BIO_free(bio);
     WOLFPROV_LEAVE(WP_LOG_COMP_PROVIDER, __FILE__ ":" WOLFPROV_STRINGIZE(__LINE__),
         ok);
diff --git a/src/wp_kbkdf.c b/src/wp_kbkdf.c
index b96f429a..7b595cb6 100644
--- a/src/wp_kbkdf.c
+++ b/src/wp_kbkdf.c
@@ -402,6 +402,9 @@ static int wp_kbkdf_init_hmac(wp_KbkdfCtx* ctx, unsigned char* key,
         }
     }
 
+    /* localKey holds a copy of the secret KDF key. */
+    OPENSSL_cleanse(localKey, sizeof(localKey));
+
     WOLFPROV_LEAVE(WP_LOG_COMP_KDF, __FILE__ ":" WOLFPROV_STRINGIZE(__LINE__), ok);
     /* Use rc style return */
     return (ok == 1) ? 0 : -1;
@@ -683,6 +686,9 @@ static int wp_kdf_kbkdf_derive(wp_KbkdfCtx* ctx, unsigned char* key,
         wp_kbkdf_mac_free(ctx);
     }
 
+    /* k_i holds derived key block(s) (and feedback state). */
+    OPENSSL_cleanse(k_i, sizeof(k_i));
+
     WOLFPROV_LEAVE(WP_LOG_COMP_KDF, __FILE__ ":" WOLFPROV_STRINGIZE(__LINE__), ok);
     return ok;
 }
diff --git a/src/wp_krb5kdf.c b/src/wp_krb5kdf.c
index b1eda69e..a2ec853c 100644
--- a/src/wp_krb5kdf.c
+++ b/src/wp_krb5kdf.c
@@ -528,6 +528,10 @@ static int wp_kdf_krb5kdf_derive(wp_Krb5kdfCtx* ctx, unsigned char* key,
 
     wc_AesFree(&aes);
 
+    /* block and cipherBlock hold derived key material. */
+    OPENSSL_cleanse(block, sizeof(block));
+    OPENSSL_cleanse(cipherBlock, sizeof(cipherBlock));
+
     WOLFPROV_LEAVE(WP_LOG_COMP_KRB5KDF, "wp_kdf_krb5kdf_derive", ok);
     return ok;
 }
diff --git a/src/wp_params.c b/src/wp_params.c
index 761123a4..b7b02308 100644
--- a/src/wp_params.c
+++ b/src/wp_params.c
@@ -63,6 +63,9 @@ int wp_mp_read_unsigned_bin_le(mp_int* mp, const unsigned char* data,
         }
     }
 
+    /* rdata may hold private key material (RSA d/p/q, EC/DH private). */
+    OPENSSL_cleanse(rdata, sizeof(rdata));
+
     WOLFPROV_LEAVE(WP_LOG_COMP_PROVIDER, __FILE__ ":" WOLFPROV_STRINGIZE(__LINE__), ok);
     return ok;
 }
diff --git a/src/wp_rsa_kmgmt.c b/src/wp_rsa_kmgmt.c
index c65f09f5..becaa404 100644
--- a/src/wp_rsa_kmgmt.c
+++ b/src/wp_rsa_kmgmt.c
@@ -3316,6 +3316,10 @@ static int wp_rsa_encode_enc_pki(const wp_RsaEncDecCtx* ctx, const wp_Rsa* rsa,
         }
     }
 
+    /* encodedKey holds the plaintext PKCS#8 private key before encryption. */
+    if (encodedKey != NULL) {
+        OPENSSL_cleanse(encodedKey, len);
+    }
     XFREE(encodedKey, NULL, DYNAMIC_TYPE_RSA_BUFFER);
 
     OPENSSL_cleanse(password, sizeof(password));
@@ -4276,7 +4280,7 @@ static int wp_rsa_encode_text_format_hex(BIO *out, const mp_int* num,
     }
     else if (mp_to_unsigned_bin((mp_int*)num, binData) != MP_OKAY) {
         ok = 0;
-        OPENSSL_free(binData);
+        OPENSSL_clear_free(binData, binLen);
         binData = NULL;
     }
     else {
@@ -4315,7 +4319,8 @@ static int wp_rsa_encode_text_format_hex(BIO *out, const mp_int* num,
             }
         }
 
-        OPENSSL_free(binData);
+        /* binData may hold private CRT components (d/p/q/dP/dQ/u). */
+        OPENSSL_clear_free(binData, binLen);
         binData = NULL;
     }
 
diff --git a/src/wp_seed_src.c b/src/wp_seed_src.c
index 3e9ac97b..49268853 100644
--- a/src/wp_seed_src.c
+++ b/src/wp_seed_src.c
@@ -657,14 +657,14 @@ static size_t wp_seed_src_get_seed(wp_SeedSrcCtx* ctx, unsigned char** pSeed,
     if (rc != (int)minLen) {
         WOLFPROV_MSG_DEBUG_RETCODE(WP_LOG_LEVEL_DEBUG,
             "wp_urandom_read failed", rc);
-        OPENSSL_free(buffer);
+        OPENSSL_clear_free(buffer, minLen);
         buffer = NULL;
         goto end;
     }
 
     /* Mix in additional input if provided */
     if (!wp_seed_src_adin_mix_in(buffer, minLen, addIn, addInLen)) {
-        OPENSSL_free(buffer);
+        OPENSSL_clear_free(buffer, minLen);
         buffer = NULL;
         goto end;
     }