quiche v. 0.15.0 through 0.19.0 was discovered to be vulnerable to unbounded queuing of path validation messages, which could lead to excessive resource consumption. QUIC path validation (RFC 9000 Section 8.2) requires that the recipient of a PATHCHALLENGE frame responds by sending a PATHRESPONSE. An unauthenticated remote attacker can exploit the vulnerability by sending PATHCHALLENGE frames and manipulating the connection (e.g. by restricting the peer's congestion window size) so that PATHRESPONSE frames can only be sent at the slower rate than they are received; leading to storage of path validation data in an unbounded queue. Quiche versions greater than 0.19.0 address this problem.