EUVD-2026-39575
GHSA-gq94-hf88-g4wv
Severity by source
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
AV:N for TLS network reachability; AC:H for non-default compile flags and explicit API calls required; PR:N as any client can open a TLS session; I:H for full authentication bypass.
Primary rating from Vendor (wolfSSL).
CVSS VectorVendor: wolfSSL
Lifecycle Timeline
2DescriptionCVE.org
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.
AnalysisAI
Post-handshake authentication bypass in wolfSSL TLS 1.3 permits a connected client to skip certificate verification during server-initiated post-handshake re-authentication. When a server has issued a post-handshake CertificateRequest via wolfSSL_request_certificate(), a client can send a Finished message without providing a Certificate or CertificateVerify; the server incorrectly applies an initial-handshake exemption and accepts it, treating the client as authenticated. No public exploit is identified and this is not listed in CISA KEV; the vulnerability was self-disclosed by wolfSSL with a patch available in GitHub PR #10702.
Technical ContextAI
wolfSSL is a lightweight, portable TLS library (CPE: cpe:2.3:a:wolfssl:wolfssl:*:*:*:*:*:*:*:*) widely deployed in embedded, IoT, automotive, and networking products. The defect (CWE-287: Improper Authentication) is located in src/tls13.c within DoTls13Finished() and SanityCheckTls13MsgReceived(). TLS 1.3 post-handshake authentication (PHA, RFC 8446 §4.6.2) allows a server to request client certificate authentication after the initial handshake via a CertificateRequest message. wolfSSL tracks an outstanding PHA request via the certReqCtx pointer. The bug: the code path that exempts an absent/empty client certificate - intended only for the initial handshake when FAIL_IF_NO_PEER_CERT is not set - was also applied while certReqCtx was non-NULL, meaning an outstanding PHA CertificateRequest was being treated identically to an optional-cert initial handshake. The PR diff confirms the fix narrows this exemption: the condition now reads (!ssl->options.verifyPostHandshake || ssl->certReqCtx != NULL), so that when certReqCtx is set the server re-mandates Certificate and CertificateVerify before accepting Finished.
RemediationAI
Apply the upstream fix from GitHub PR #10702 (https://github.com/wolfSSL/wolfssl/pull/10702) and monitor https://www.wolfssl.com/docs/security-vulnerabilities/ for the official patched release version, which is not yet confirmed from available data - do not assume the PR merge corresponds to a tagged release. If an immediate upgrade is not feasible, the most direct and lowest-risk compensating control is to recompile wolfSSL without the --enable-postauth (or --enable-all) flag, removing the WOLFSSL_POST_HANDSHAKE_AUTH define entirely; this eliminates the vulnerable code path with no impact on servers that do not require post-handshake re-authentication. Alternatively, removing calls to wolfSSL_request_certificate() from server application code is sufficient to prevent exploitation without recompilation, though it also disables the PHA feature. Servers that do not use post-handshake authentication in any form require no action.
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Same weakness CWE-287 – Improper Authentication
View allSame technique Authentication Bypass
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External POC / Exploit Code
Leaving vuln.today