GHSA-hwqm-qvj9-4jr2: gosaml2 CBC Padding Panic — Unauthenticated Process Crash

The AES-CBC decryption path in DecryptBytes() panics on crafted ciphertext whose plaintext is all zero bytes. After decryption, bytes.TrimRight(data, "\x00") empties the slice, then data[len(data)-1] panics with index out of range [-1]. There is no recover() in the library. The panic propagates through ValidateEncodedResponse and kills the goroutine (or the entire process in non-net/http servers). An attacker needs only the SP’s public RSA key (published in SAML metadata) to construct the payload — no valid signature is required.