CVE-2026-6331 — 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…
Published: 2026-06-25 · CVSS: 2.1 · CVSS 4.0
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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7