CVE-2026-55962
CVE-2026-55962 · TLS 1.3 post-handshake authentication: server accepts Finished without client Certificate/CertificateVerify
This page contains facts from public vulnerability sources. Check the original advisory before updating.
TLS 1.3 post-handshake authentication (PHA) issue where a server could accept a client's Finished message without the client having sent a Certificate and CertificateVerify. The post-handshake-auth exemption that allows an empty/absent peer certificate was only intended for the initial handshake, but it was also being applied while a post-handshake CertificateRequest was still outstanding. The check is now scoped to the initial handshake only: on the server, once a post-handshake CertificateRequest has been sent (certReqCtx is set), a peer certificate and a valid CertificateVerify are required again before the Finished is accepted, with empty-certificate handling following the configured verify mode (FAIL_IF_NO_PEER_CERT) just as during first-handshake client authentication. Only affects TLS 1.3 servers built with post-handshake authentication support (WOLFSSL_POST_HANDSHAKE_AUTH / --enable-postauth, included in --enable-all) that enable WOLFSSL_VERIFY_POST_HANDSHAKE and request a client certificate after the handshake via wolfSSL_request_certificate(). Clients, and servers that do not use post-handshake authentication, are unaffected.
CVSS 6.0 · Medium · EPSS 0.2% · Fix available
- Published
- Updated
Stack: system
Affected products and versions
wolfssl
- Versions
- ≥ 5.5.4, ≤ 5.9.1: Affected (semver)
No fix published
wolfssl Debian:12
- Versions
- 5.5.4-2
- 5.5.4-2+deb12u1
- 5.5.4-2+deb12u2
- Affected ranges
- ECOSYSTEM: < 5.5.4-2+deb12u3
Update to 5.5.4-2+deb12u3
wolfssl Debian:13
- Versions
- 5.7.2-0.1
- 5.7.2-0.1+deb13u1
- Affected ranges
- ECOSYSTEM: < 5.7.2-0.1+deb13u2
Update to 5.7.2-0.1+deb13u2
wolfssl Ubuntu:16.04:LTS
- Versions
- 3.4.8+dfsg-1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
wolfssl Ubuntu:18.04:LTS
- Versions
- 3.10.2+dfsg-2
- 3.12.0+dfsg-1
- 3.12.2+dfsg-1
- 3.13.0+dfsg-1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
wolfssl Ubuntu:20.04:LTS
- Versions
- 4.1.0+dfsg-2
- 4.2.0+dfsg-1
- 4.2.0+dfsg-2
- 4.2.0+dfsg-3
- 4.3.0+dfsg-2
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
wolfssl Ubuntu:22.04:LTS
- Versions
- 4.6.0-3
- 5.0.0-1
- 5.1.1-1
- 5.2.0-1
- 5.2.0-2
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
wolfssl Ubuntu:24.04:LTS
- Versions
- 5.5.4-2
- 5.5.4-2.1
- 5.6.4-2
- 5.6.6-1.2
- 5.6.6-1.3
- 5.6.6-1.3build1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
wolfssl Ubuntu:25.10
- Versions
- 5.7.2-0.1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
wolfssl Ubuntu:26.10
- Versions
- 5.9.1-0.1
- 5.9.2-1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
wolfssl Ubuntu:26.04:LTS
- Versions
- 5.7.2-0.1
- 5.8.2-1.2
- 5.8.4-1
- 5.9.1-0.1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published