CVE-2025-64763

A flaw was found in Envoy. This vulnerability allows a de-synchronized CONNECT tunnel state via accepting client data before issuing a 2xx response and forwarding it to the upstream TCP Transmission Control Protocol connection when configured in TCP Transmission Control Protocol proxy mode to...

Envoy forwards early CONNECT data in TCP proxy mode

Summary Forwarding of early CONNECT data in TCP proxy mode. Details Per RFC 7231-4.3.6 the sender of CONNECT and all inbound proxies switch to tunnel mode only after receiving 2xx response. However in TCP proxy mode, Envoy accepts client data before it has issued a 2xx response and eagerly proxie...

CVE-2025-64763: Protection Mechanism Failure

Envoy is a high-performance edge/middle/service proxy. In 1.33.12, 1.34.10, 1.35.6, 1.36.2, and earlier, when Envoy is configured in TCP proxy mode to handle CONNECT requests, it accepts client data before issuing a 2xx response and forwards that data to the upstream TCP connection. If a forwardi...