Out-of-Bounds Heap Read in wolfSSL during Certificate Signature Verification
CVE-2026-12340

6.3MEDIUM

Key Information:

Vendor

Wolfssl

Status
Wolfssl
Vendor
CVE Published:
25 June 2026

What is CVE-2026-12340?

A vulnerability in wolfSSL can lead to an out-of-bounds heap read during the verification of SM2/SM3 certificate signatures. The issue arises when a certificate containing an SM3wSM2 signature is processed. If the public key associated with the certificate is shorter than 65 bytes, the computation of the Subject Key Identifier accesses memory beyond the limit of the key, resulting in potential crashes due to denial of service. This vulnerability specifically affects builds configured with SM2 support.

Affected Version(s)

wolfSSL 5.6.4 <= 5.9.1

References

https://github.com/wolfSSL/wolfssl/pull/10641
patch
https://www.wolfssl.com/docs/security-vulnerabilities/

CVSS V4

Score:
6.3
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
Physical
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

David Pokora, Trail of Bits (in collaboration with Anthropic)
.