{"id":"UBUNTU-CVE-2026-55962","details":"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.","modified":"2026-06-29T23:19:15.089064782Z","published":"2026-06-25T22:17:00Z","upstream":["CVE-2026-55962"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-55962"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-55962"},{"type":"REPORT","url":"https://github.com/wolfSSL/wolfssl/pull/10702"},{"type":"REPORT","url":"https://github.com/wolfSSL/wolfssl/pull/10702"},{"type":"REPORT","url":"https://www.wolfssl.com/docs/security-vulnerabilities/"}],"affected":[{"package":{"name":"wolfssl","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/wolfssl?arch=source&distro=xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.4.8+dfsg-1"],"ecosystem_specific":{"binaries":[{"binary_version":"3.4.8+dfsg-1","binary_name":"libcyassl5"},{"binary_name":"libwolfssl0","binary_version":"3.4.8+dfsg-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55962.json"}},{"package":{"name":"wolfssl","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/wolfssl?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.10.2+dfsg-2","3.12.0+dfsg-1","3.12.2+dfsg-1","3.13.0+dfsg-1"],"ecosystem_specific":{"binaries":[{"binary_version":"3.13.0+dfsg-1","binary_name":"libwolfssl15"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55962.json"}},{"package":{"name":"wolfssl","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/wolfssl?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"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"],"ecosystem_specific":{"binaries":[{"binary_version":"4.3.0+dfsg-2","binary_name":"libwolfssl24"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55962.json"}},{"package":{"name":"wolfssl","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/wolfssl?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.6.0-3","5.0.0-1","5.1.1-1","5.2.0-1","5.2.0-2"],"ecosystem_specific":{"binaries":[{"binary_name":"libwolfssl32","binary_version":"5.2.0-2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55962.json"}},{"package":{"name":"wolfssl","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/wolfssl?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"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"],"ecosystem_specific":{"binaries":[{"binary_name":"libwolfssl42t64","binary_version":"5.6.6-1.3build1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55962.json"}},{"package":{"name":"wolfssl","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/wolfssl?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.7.2-0.1"],"ecosystem_specific":{"binaries":[{"binary_version":"5.7.2-0.1","binary_name":"libwolfssl42t64"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55962.json"}},{"package":{"name":"wolfssl","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/wolfssl?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.7.2-0.1","5.8.2-1.2","5.8.4-1","5.9.1-0.1"],"ecosystem_specific":{"binaries":[{"binary_version":"5.9.1-0.1","binary_name":"libwolfssl44"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55962.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N"},{"type":"Ubuntu","score":"medium"}]}