PHP JWT Framework: JWSVerifier uses algorithm from unprotected header, enabling algorithm confusion attacks
JWSVerifier::getAlgorithm() in src/Library/Signature/JWSVerifier.php (line 144) merges protected and unprotected headers using PHP's spread operator: $completeHeader = […$signature->getProtectedHeader(), …$signature->getHeader()]; In PHP, when spreading arrays with duplicate string keys, the last array's values take precedence. Since the unprotected header (getHeader()) is spread second, an attacker can override the integrity-protected alg parameter by placing a different value in the unprotected header. This creates a Time-of-Check/Time-of-Use (TOCTOU) vulnerability: HeaderCheckerManager validates alg from the protected …