CVE-2026-94419 Client session cache reference poisoning allows resumption with wrong server
Attackers can hijack TLS sessions by poisoning the client cache, bypassing certificate verification and impersonating servers in wolfSSL builds with default session caching enabled.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-94419?
CVE-2026-94419 is a low-severity authentication bypass vulnerability in Wolfssl Wolfssl, published on 27 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
Without NO_SESSION_CACHE_REF, wolfSSL_get_session() does not return a session object but a ClientSession reference of the form {row, index, hash(sessionID)} into the process-global SessionCache, and ClientSessionToSession() validates it against that hash alone. Because the TLS 1.2 session ID is chosen by the server and sent in clear, AddSessionToCache() matches any other server's session on the same ID and overwrites the client-side entry with that server's master secret, cipher suite and version, while the handle continues to resolve; nothing on the write path compares the peer, the application's server ID or the WOLFSSL_CTX. Resuming through the handle then produces an abbreviated handshake in which no Certificate message is sent, so neither chain verification nor wolfSSL_check_domain_name() runs, and the attacker is accepted as the original server for the whole of that connection. Affected builds are those leaving NO_SESSION_CACHE_REF, NO_SESSION_CACHE, NO_CLIENT_CACHE and TITAN_SESSION_CACHE all undefined, which includes a plain ./configure, --enable-opensslextra and --enable-opensslall; fifteen integration options define NO_SESSION_CACHE_REF and are therefore not affected, among them --enable-all, --enable-distro, --enable-curl, --enable-nginx, --enable-haproxy, --enable-stunnel, --enable-wpas and the rest of the OPENSSL_COMPATIBLE_DEFAULTS family, and --enable-leanpsk, --enable-leantls, --enable-lowresource and --enable-tinytls13 disable the cache outright. The application must use the legacy reference flow, wolfSSL_get_session() or SSL_get_session() followed by wolfSSL_set_session(); wolfSSL_get1_session() returns the session object itself and is not affected, nor are wolfSSL_SetServerID() lookups. Only TLS 1.2 and below and DTLS 1.2 and below are reachable, since TLS 1.3 and ticket resumption with an empty ServerHello session ID both use a client-chosen cache key. The poisoned entry lives in the process-global cache, so it crosses WOLFSSL_CTX boundaries and persists until the entry is evicted or the session times out, 500 seconds by default. Releases v5.3.0 through v5.9.2 are affected; the fix adds a per-write generation counter to the cache and raises WOLFSSL_CACHE_VERSION from 2 to 3, so a cache persisted by an older build is rejected by a fixed one.
Weakness: CWE-287
Which versions are affected by CVE-2026-94419?
It affects 1 product.
Products include Wolfssl Wolfssl.
How do I fix CVE-2026-94419?
No fix has been published for CVE-2026-94419 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-94419 being exploited?
There is no known exploitation of CVE-2026-94419 in the wild and no public exploit code.
Other vulnerabilities in Wolfssl Wolfssl
Sources
Also known as AZL-105185, DEBIAN-CVE-2026-94419, GHSA-c72q-45p9-v8qh, UBUNTU-CVE-2026-94419.