Opal Wright

An inefficient algorithmic complexity issue exists in the QUIC stream reassembly process. OpenSSL uses a doubly-linked list to manage received QUIC stream fragments; while append operations are optimized, any fragment that does not immediately follow the current `tail` triggers a head-to-tail linear search. A remote peer that has completed the handshake can manipulate the sequence of offsets using compliant STREAM frames within the advertised receive window to force the server into O(n^2) operations. This results in progressive performance deterioration and excessive CPU pressure, potentially leading to a Denial of Service with low attacker bandwidth.

When processing QUIC traffic, the QUIC stack may retain metadata for ACK-only packets for the entire duration of a connection if a peer repeatedly sends ack-eliciting packets without acknowledging the ACK-only responses. A remote peer that completes a QUIC handshake can exploit this by sending numerous PING frames to force the generation of ACK-only packets while withholding acknowledgments for ack-eliciting data. This behavior causes connection-scoped memory growth, which can lead to a Denial of Service through memory exhaustion, particularly during sustained traffic or across many concurrent QUIC connections.