Executive brief
wolfSSL is a security library used to encrypt communications for various applications and devices. A flaw was found where the library failed to properly verify certain connection details (SNI and ALPN) when resuming a previously established secure session. This could allow an attacker to reuse an authenticated session in a different context where they should not have access, potentially bypassing security policies that differ between virtual hosts.
Technical details
A vulnerability exists in wolfSSL's TLS 1.2 and 1.3 session resumption logic. Specifically, stateful (session-ID) resumption previously skipped the binding checks for Server Name Indication (SNI) and Application-Layer Protocol Negotiation (ALPN) that were already implemented for ticket-based resumption. An attacker with a valid cached session could resume that session under a different SNI or ALPN than originally negotiated. In environments where client-authentication policies vary across virtual hosts, this allows the cached peer-authentication state to be applied to a context for which it was not established. The fix ensures resumption verifies SNI/ALPN bindings for all paths and falls back to a full handshake on mismatch.
Affected products
- wolfSSL wolfSSL 3.15.0 through 5.9.1
Timeline
- 2026-05-14: disclosed: Initial pull request submitted to wolfSSL GitHub
- 2026-06-05: patched: Fix merged into wolfSSL master branch
- 2026-06-25: advisory: CVE-2026-11703 published