CVE-2026-115906: zip: AES Entry HMAC Authentication Bypass on Premature EOF

An AES-encrypted (AE-x) entry’s authentication code is verified only when the reader’s byte counter lands exactly on zero. If the bounded entry reader reaches the archive’s actual EOF before the attacker-controlled, header-declared compressed_size, the counter remains positive, the HMAC is never read or compared, and the truncated, unauthenticated plaintext is returned as a clean end of stream. A zero-payload entry also returns before authentication. An attacker who does not know the password can modify an archive so chosen or modified plaintext is accepted with no error.