wolfSSL up to 5.9.0 KeyShare src/tls.c TLSX_KeyShare_ProcessPqcHybridClient use after free

Summaryinfo

A vulnerability marked as critical has been reported in wolfSSL up to 5.9.0. The impacted element is the function TLSX_KeyShare_ProcessPqcHybridClient of the file src/tls.c of the component KeyShare Handler. The manipulation leads to use after free. This vulnerability is traded as CVE-2026-5460. It is possible to initiate the attack remotely. There is no exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in wolfSSL up to 5.9.0. It has been rated as critical. This issue affects the function TLSX_KeyShare_ProcessPqcHybridClient of the file src/tls.c of the component KeyShare Handler. The manipulation with an unknown input leads to a use after free vulnerability. Using CWE to declare the problem leads to CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. Impacted is integrity, and availability. The summary by CVE is:

A heap use-after-free exists in wolfSSL's TLS 1.3 post-quantum cryptography (PQC) hybrid KeyShare processing. In the error handling path of TLSX_KeyShare_ProcessPqcHybridClient() in src/tls.c, the inner function TLSX_KeyShare_ProcessPqcClient_ex() frees a KyberKey object upon encountering an error. The caller then invokes TLSX_KeyShare_FreeAll(), which attempts to call ForceZero() on the already-freed KyberKey, resulting in writes of zero bytes over freed heap memory.

The weakness was shared by Calvin Young. It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-5460 since 04/03/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 305910 (Linux Distros Unpatched Vulnerability : CVE-2026-5460), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.9.1 eliminates this vulnerability. Applying a patch is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (305910). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Name

• wolfSSL

Version

• 5.0
• 5.1
• 5.2
• 5.3
• 5.4
• 5.5
• 5.6
• 5.7
• 5.8
• 5.9.0

License

• open-source

Website

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

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