Vulnerability in Wolfssl
CVE-2026-6331
HMAC zero-length tag forgery in EVP_DigestVerifyFinal, where a zero-length tag could be accepted as valid during HMAC verification. In the OpenSSL-compatibility HMAC verify path the supplied signature length was only checked as not exceeding the MAC length, so a zero-length or otherwise truncated tag could pass verification. The fix requires the supplied tag length to exactly equal the MAC length and rejects a zero-length MAC, so a forged short or empty tag is no longer accepted.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
EPSS exploit prediction
EPSS: 0.002 (7.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 8th percentile — 7.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000
Affected products
- Wolfssl — versions 3.15.5
Weakness classification (CWE)
References
- github.com/wolfSSL/wolfssl/pull/10192 (Patch, patch, Issue Tracking)
- www.wolfssl.com/docs/security-vulnerabilities/ (Vendor Advisory)
Frequently asked questions
- What is CVE-2026-6331?
- CVE-2026-6331 is a high-severity vulnerability in Wolfssl, classified under Improper Verification of Cryptographic Signature. CVSS score: 7.5/10. Published 2026-06-25.
- How severe is CVE-2026-6331?
- High severity. CVSS v3 base score is 7.5 out of 10.