Executive Summary

This vulnerability is an HMAC zero-length tag forgery issue in the EVP_DigestVerifyFinal function. It occurs because the verification process accepted a zero-length or truncated HMAC tag as valid. Specifically, the OpenSSL-compatible HMAC verification path only checked that the supplied signature length did not exceed the MAC length, allowing a zero-length or shortened tag to pass verification incorrectly.

The fix for this vulnerability requires that the supplied tag length exactly matches the MAC length and rejects any zero-length MAC tags, preventing forged short or empty tags from being accepted.

Useful 0 Not Useful 0

Impact Analysis

This vulnerability can allow an attacker to forge an HMAC tag by providing a zero-length or truncated tag that is incorrectly accepted as valid. This undermines the integrity verification of messages or data protected by HMAC, potentially allowing unauthorized data to be accepted as authentic.

Useful 0 Not Useful 0