CVE-2026-93304: wolfSSL TLS 1.2 ChangeCipherSpec message ordering bypass

CVE-2026-93304 · Severity: info · Published 2026-09-27

wolfSSL is a cryptographic library used to secure network communications in embedded systems and applications. A flaw allows an attacker to complete a TLS handshake by sending an out-of-order message before the client has finished its key exchange, potentially enabling the attacker to inject malicious data the client accepts as legitimate. For connections using pre-shared keys, any attacker can exploit this without possessing the key; for certificate-based connections, the attacker must be positioned between the client and server.

Technologies: Wolfssl. Vendors: Wolfssl.

Quick answers

Is CVE-2026-93304 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-93304 being exploited in the wild.
How severe is CVE-2026-93304?
Informational severity, published 27 September 2026.
Which products and versions are affected?
wolfSSL wolfSSL.
Is there a fix for CVE-2026-93304?
A patch was published on 2026-09-18: Fix merged in PR #11458 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-93304 attacked?
It is attacked over the network or from the adjacent network, in a software library.
Am I affected by CVE-2026-93304?
Check whether you run Wolfssl. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A (D)TLS 1.2 client incorrectly accepts a ChangeCipherSpec message before the ClientKeyExchange has been sent, allowing the attacker to derive read keys from known deterministic values and complete the handshake impersonating the server. DTLS clients are vulnerable when a single datagram delivers out-of-order records; TLS clients are vulnerable when the application uses wolfSSL_inject() or enables read-ahead buffering. The attacker cannot decrypt the client's traffic (which uses correct keys), but can send authenticated data, and the legitimate server never completes the handshake. A fix has been merged as of 18 September 2026.

Affected products

  • wolfSSL wolfSSL

Timeline

  • 2026-09-18: patched: Fix merged in PR #11458

References

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