WolfSSL: Five Vulnerabilities Disclosed Together Affecting Certificate Validation and Crypto Operations
Key findings • Five vulnerabilities disclosed simultaneously in WolfSSL on July 27, 2026. • Flaws include wildcard certificate bypass, OCSP serial number confusion, and trust-chain issues. …
Key findings
- Five vulnerabilities disclosed simultaneously in WolfSSL on July 27, 2026.
- Flaws include wildcard certificate bypass, OCSP serial number confusion, and trust-chain issues.
- ML-KEM implementation and session resumption bindings were also affected.
- Vulnerabilities patched in WolfSSL version 5.7.0 and Debian updates.
On July 27, 2026, a batch of five vulnerabilities was disclosed in the WolfSSL embedded SSL/TLS library, affecting Debian's packaging of the software. These vulnerabilities span various aspects of certificate validation and cryptographic operations, with potential impacts ranging from trust-chain bypasses to improper handling of cryptographic parameters. The disclosures highlight potential weaknesses in how WolfSSL processes wildcard certificates, OCSP responses, and advanced cryptographic schemes like ML-KEM.
One significant vulnerability, CVE-2026-10592, concerns the bypass of Certificate Authority (CA) name-constraint checks when certificates feature wildcard DNS Subject Alternative Names (SANs). This could allow a certificate with a wildcard SAN, which should be rejected by the CA's constraints, to be accepted. This bypass could undermine the trust model for certificate issuance and validation.
Another critical finding, CVE-2026-11310, details an X.509 trust-chain bypass within WolfSSL's OpenSSL compatibility certificate verifier. This specific vulnerability affects builds configured with --enable-opensslextra (OPENSSL_EXTRA) and where applications manually validate certificates using caller-supplied intermediate certificates. It could lead to the acceptance of untrusted certificate chains.
The batch also includes CVE-2026-10098, which points to a length-confusion issue in the OCSP (Online Certificate Status Protocol) CertID serial-number comparison. This flaw in wolfSSL_OCSP_resp_find_status could result in a same-issuer SingleResponse being incorrectly associated with the revocation status of a different certificate if its serial number is a prefix of the target certificate's serial number.
Furthermore, CVE-2026-10097 addresses a flaw in WolfSSL's AVX2-optimized ML-KEM implementation, specifically mlkem_cmp_avx2. During ML-KEM-1024 decapsulation, only 1536 out of 1568 ciphertext bytes are compared in the Fujisaki-Okamoto re-encryption check. This oversight allows ciphertexts that differ in the latter bytes to bypass implicit rejection and be accepted as valid.
Finally, CVE-2026-11703 highlights a missing Server Name Indication (SNI) and Application-Layer Protocol Negotiation (ALPN) binding during stateful (session-ID) resumption. This contrasts with ticket-based resumption, which does perform this binding. Consequently, a cached session could be resumed with a different SNI/ALPN than originally negotiated, potentially carrying over cached client-authentication policies across different virtual hosts where such policies vary.
These vulnerabilities were disclosed simultaneously on July 27, 2026. Users of WolfSSL, particularly those relying on Debian's packaged versions, are advised to review the specific CVE details and apply any available patches or mitigations provided by the WolfSSL project and Debian. The simultaneous disclosure suggests a coordinated effort to address these distinct security concerns within the library. The implications of these flaws underscore the importance of rigorous testing and validation in cryptographic libraries, especially those used in embedded systems where security is paramount.
The vulnerabilities were patched in WolfSSL version 5.7.0. Debian has released updated packages incorporating these fixes. Users should ensure they are running a patched version to mitigate these risks. The affected versions in Debian's packaging are typically those prior to the security updates.
The simultaneous disclosure of these five distinct vulnerabilities in WolfSSL warrants prompt attention from developers and system administrators utilizing the library. The varied nature of the flaws, from certificate validation bypasses to cryptographic implementation errors, emphasizes the need for comprehensive security practices and timely updates. Staying informed about security advisories from both WolfSSL and distribution maintainers like Debian is crucial for maintaining a secure environment.