GoAhead Web Server TLS Vulnerabilities Enable Revoked Certificate Authentication and Session Decryption

Security researchers have identified two TLS-related vulnerabilities in the GoAhead Web Server. The first flaw involves a certificate revocation list being loaded into the OpenSSL backend but revocation checking remaining disabled, allowing revoked client certificates to pass authentication. The second flaw permits session decryption due to missing integrity checks in the OpenSSL backend when mutual-TLS is configured. Both issues require an active CRL and mutual-TLS setup to be exploitable.

The GoAhead embedded web server loaded a certificate revocation list into its default TLS backend but never turned revocation checking on, so a revoked client certificate could still pass login on affected setups. The flaw is in builds that use the OpenSSL backend with mutual-TLS, where the server checks a client certificate and vice versa, and a revocation list is configured to block revoked certificates.

The second issue relates to session decryption. Due to missing integrity checks in the OpenSSL backend with mutual-TLS configuration, an attacker with network access may be able to decrypt TLS sessions on affected deployments. This could expose sensitive data transmitted over HTTPS connections in embedded devices, IoT gateways, and on-premises web servers running GoAhead.

Both vulnerabilities require mutual-TLS configuration and an active Certificate Revocation List (CRL) to be present. Users without mutual-TLS or without a configured CRL are not affected. GoAhead has not assigned CVE identifiers at the time of reporting, and no public exploit code has been confirmed. The researcher who reported the issues stated that exploitation requires network access and the ability to present revoked client certificates or intercept TLS handshakes.

Affected products include GoAhead Web Server versions used in embedded systems, IoT devices, and embedded web applications. The vulnerabilities were reported publicly on October 27, 2026, via The Hacker News. GoAhead security advisories should be consulted for version-specific fixes and configuration guidance for enabling certificate revocation checking and applying integrity protections to TLS handshakes.