Executive brief
wolfSSL, a cryptographic library used by many network applications, has a flaw in how it validates SSL/TLS certificates when both OCSP and CRL revocation checking are enabled. An attacker could present a certificate that should have been rejected as revoked, causing the application to accept it as valid. This affects long-running processes and could allow unauthorized access or man-in-the-middle attacks.
Technical details
When OCSP and CRL revocation checks are both enabled on a WOLFSSL_CTX or certificate manager, the library incorrectly treats a missing OCSP responder as a successful OCSP result, skipping the CRL fallback check. This allows revoked certificates to be accepted if they lack an Authority Information Access OCSP URL. The vulnerability exists in ProcessPeerCerts() and is reachable over all supported TLS versions (1.0–1.3) and DTLS for both client and server certificate verification.
Affected products
- wolfSSL wolfSSL 5.9.2 and earlier
Timeline
- 2026-09-27: disclosed