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.
3.4.8+dfsg-13.10.2+dfsg-23.12.0+dfsg-13.12.2+dfsg-13.13.0+dfsg-14.1.0+dfsg-24.2.0+dfsg-14.2.0+dfsg-24.2.0+dfsg-34.3.0+dfsg-25.7.2-0.1Exploitability
AV:LAC:HAT:PPR:NUI:NVulnerable System
VC:NVI:LVA:NSubsequent System
SC:NSI:NSA:NCVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N