wolfSSL up to 5.9.2 ChangeCipherSpec wolfSSL_inject input validation

Summaryinfo

A vulnerability labeled as critical has been found in wolfSSL up to 5.9.2. The impacted element is the function wolfSSL_inject of the component ChangeCipherSpec Handler. The manipulation results in input validation. This vulnerability was named CVE-2026-93304. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability classified as critical has been found in wolfSSL up to 5.9.2. Affected is the function wolfSSL_inject of the component ChangeCipherSpec Handler. The manipulation with an unknown input leads to a input validation vulnerability. CWE is classifying the issue as CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. This is going to have an impact on integrity, and availability. CVE summarizes:

A (D)TLS 1.2 client can accept a ChangeCipherSpec message before it has sent its ClientKeyExchange. No master secret has been derived at that point, so the client installs read keys derived from a known (deterministic) key and checks the server's Finished against that same key. An out-of-order ChangeCipherSpec can therefore be used by an attacker to complete the handshake in place of the server and send data the client accepts as authentic. The client's own traffic still uses correctly derived keys, so the attacker cannot read it, and the genuine server never completes the handshake. DTLS 1.2 clients are exposed because a datagram read can deliver the out-of-order records on its own. TLS 1.2 clients are exposed when the application supplies received bytes with wolfSSL_inject() or enables read ahead. For certificate suites, the attacker must be in a man-in-the-middle position. For PSK (Pre Shared Key) connections, any fake server can succeed without knowing the PSK.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-93304 since 09/17/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 09/27/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Name

• wolfSSL

Version

• 5.9.0
• 5.9.1
• 5.9.2

License

• open-source

Website

• Product: https://github.com/wolfSSL/wolfssl/

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