wolfSSL up to 5.9.2 Certificate Signature Verification wolfssl/test.h ProcessPeerCertParse certificate validation

Summaryinfo

A vulnerability marked as problematic has been reported in wolfSSL up to 5.9.2. Impacted is the function ProcessPeerCertParse of the file wolfssl/test.h of the component Certificate Signature Verification. The manipulation leads to certificate validation. This vulnerability is referenced as CVE-2026-94418. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability was found in wolfSSL up to 5.9.2 and classified as problematic. This issue affects the function ProcessPeerCertParse of the file wolfssl/test.h of the component Certificate Signature Verification. The manipulation with an unknown input leads to a certificate validation vulnerability. Using CWE to declare the problem leads to CWE-295. The product does not validate, or incorrectly validates, a certificate. Impacted is integrity. The summary by CVE is:

Under WOLFSSL_SMALL_CERT_VERIFY, ProcessPeerCertParse() runs the certificate signature check separately from the parse to keep peak memory down, then merges the two results, but it merged the signature result back only when the parse returned 0, so any parse error hid it. ParseCertRelative() reaches its validity-date, name-constraint and critical-extension checks only after ConfirmSignature() has passed, so splitting the signature check out inverts the precedence that makes "override date errors" a sound policy, and ASN_SIG_CONFIRM_E is never surfaced anywhere. The attacker needs no key material from the real PKI and no CA compromise: a self-made certificate carrying the expected subject name, the trusted CA's subject as its issuer, arbitrary bytes where the signature goes, a validity window in the past and the attacker's own key pair is sufficient. Affected builds define WOLFSSL_SMALL_CERT_VERIFY, which is off by default, is not set implicitly by any platform or preset header, and is not reachable from any CMake option; the autotools routes are --enable-lowresource, --enable-leantls, --enable-tinytls13=cert and --enable-tinytls13=mutualauth, and examples/configs/user_settings_embedded.h reaches it through WC_CFG_SMALL_CERT_VERIFY, which ships as 0, while neither --enable-all nor --enable-distro enables it at all. The application must additionally install a verify callback through wolfSSL_CTX_set_verify() or wolfSSL_set_verify() with WOLFSSL_VERIFY_PEER that returns 1 for ASN_BEFORE_DATE_E or ASN_AFTER_DATE_E; wolfSSL ships this exact shape as myVerify() in wolfssl/test.h under VERIFY_OVERRIDE_DATE_ERR, which examples/client -D selects. An application with no callback, or whose callback returns preverify for date errors, still fails the handshake, and wolfSSL_CertManagerVerifyBuffer() and wc_CheckCertSignature() report ASN_SIG_CONFIRM_E correctly in the same binary. TLS 1.2 and TLS 1.3 are affected in both directions, and DTLS reaches the same function; where the forged certificate is a chain certificate the callback's consent causes it to be cached in the WOLFSSL_CTX certificate manager, so an exposed deployment must restart the context or the process rather than merely reconnect.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-94418 since 09/21/2026. The exploitation is known to be difficult. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 09/27/2026). The attack technique deployed by this issue is T1587.003 according to MITRE ATT&CK.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Name

• wolfSSL

Version

• 5.9.0
• 5.9.1
• 5.9.2

License

• open-source

Website

• Product: https://github.com/wolfSSL/wolfssl/

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