### Impact When a JWE uses a password-based key-encryption algorithm (`PBES2-HS256+A128KW`, `PBES2-HS384+A192KW`, `PBES2-HS512+A256KW`), `PBES2AESKW::unwrapKey()` reads the `p2c` (PBKDF2 iteration count) parameter directly from the attacker-controlled JOSE header and passes it to `hash_pbkdf2()` with **no upper bound**. The only validation performed (`checkHeaderAdditionalParameters()`) was `is_int($p2c) && $p2c > 0`. An unauthenticated attacker can craft a single JWE whose protected header se