Zero-Length HMAC Tag Forgery in wolfSSL EVP_DigestVerifyFinal
CVE-2026-6331 Published on June 25, 2026
HMAC zero-length tag forgery in EVP_DigestVerifyFinal
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.
Weakness Type
Improper Verification of Cryptographic Signature
The software does not verify, or incorrectly verifies, the cryptographic signature for data.
Products Associated with CVE-2026-6331
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Affected Versions
wolfSSL:- Version 3.15.5, <= 5.9.1 is affected.