CVE-2026-5460: Heap Use-After-Free in PQC Hybrid KeyShare Error Cleanup in wolfSSL TLS 1.3

Vulnerability summary

CVE-2026-5460 is a medium (CVSS 6.5) Use After Free vulnerability in wolfssl. EPSS estimates a 0.21% chance of exploitation in the next 30 days, higher than 11.4% of scored vulnerabilities.

Timeline

1. 09-04-2026
   PublishedVulnerability first disclosed.
2. 10-04-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-416Use After FreeThe product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.