X.509 trust-chain bypass in wolfSSL_X509_verify_cert() via untrusted intermediate anchoring

Summary

X.509 trust-chain bypass in the OpenSSL compatibility certificate verifier (wolfSSL_X509_verify_cert()). This affects only builds with --enable-opensslextra (OPENSSL_EXTRA) and whose application validates certificates by calling X509_verify_cert() with caller-supplied untrusted intermediate certificates; for those users it is critical, otherwise the library is unaffected. In particular, native wolfSSL TLS/DTLS usage is not impacted. wolfSSL's X509_verify_cert() temporarily loads each caller-supplied untrusted intermediate into the certificate manager but failed to drop them before the trusted-store check, so an untrusted intermediate could anchor the path itself. An attacker can present a chain that never reaches a configured trust anchor and have it accepted, resulting in acceptance of an attacker-controlled certificate. This is certificate verification independent of TLS (e.g. S/MIME/CMS, code/firmware signing, JWT/JWS x5c), is not specific to any key type or algorithm, and a single untrusted intermediate suffices. The default wolfSSL TLS handshake (WOLFSSL_VERIFY_PEER) is not affected; only TLS applications doing manual or deferred peer verification through this API are, which also requires --enable-sessioncerts.

Timeline

1. Jun 25, 2026, 7:38 PM UTCCVE published
2. Jun 26, 2026, 2:02 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: yes · Technical impact: partial

3. Jun 26, 2026, 2:02 PM UTCRecord last updated

Affected versions

• wolfSSL wolfSSL

  From 5.8.4 · through 5.9.1

References 2