Go-Attestation: Hash injection into trusted measurement list via unskipped SignatureHeaderSize vendor bytes in parseEfiSignatureList()

Improper Validation of Specified Index, Position, or Offset in Input vulnerability in Google go-attestation. parseEfiSignatureList() does not advance the buffer past vendor bytes before reading entries. For hashSHA256SigGUID lists, this allows attacker-controlled vendor header bytes to be appended to the trusted SHA256 hash list. A crafted TPM event log could inject arbitrary SHA256 hashes into the verifier's trusted measurement database, enabling a remote attestation verifier to accept a compromised boot state. This issue affects go-attestation: through 0.6.0.