Envoy Proxy Use After Free Vulnerability - CVE-2026-47205

Envoy is an open source edge and service proxy designed for cloud-native applications. From 1.36.0 until 1.36.9 1.37.5 and 1.38.3 a Use-After-Free (UAF) vulnerability leading to a sudden segmentation fault exists in Envoy39s ext_authz HTTP filter when processing per-route authorization overrides concurrently with rapid downstream client disconnects. During standard request lifecycles Envoy instantiates the ext_authz filter with a foundational authorization client object (client_). If a matched route dictates a dynamic per-route HTTP or gRPC authorization service override the filter generates a localized client. In the vulnerable implementation this transient client aggressively overwrote the default client_ unique pointer by executing client_ std::move(per_route_client). When a client rapidly establishes and subsequently tears down a stream (such as rapidly refreshing a protected WebSocket endpoint) the downstream triggers the ConnectionManagerImpl::doDeferredStreamDestroy() -gt ActiveStream::onResetStream() lifecycle. Envoy immediately sequences Filter::onDestroy() in an attempt to securely abort dispatched asynchronous authorization check transactions via client_-gtcancel(). By destructing the default client abruptly during initiateCall a memory lifecycle misalignment occurs within the async client manager. The stream teardown fails to reliably track and cancel the dynamically bound asynchronous authorization tasks orchestrating a sequence where a late asynchronous callback from the network evaluates against a heavily destroyed ActiveStream validation span generating a UAF process crash. This vulnerability is fixed in 1.36.9 1.37.5 and 1.38.3.