Summary Envoy's extproc HTTP filter is at risk of crashing if a local reply is sent to the external server due to the filter's life time issue. A known situation is the fail of a websocket handshake will trigger a local reply leading to the crash of Envoy.

PoC If both websocket and extproc are enabled, a failed handshake will trigger a local reply, thus extproc will crash.

Mitigation 1. Disable websocket traffic 2. Change the websocket response from backend to always return 101 Switch protocol based on RFC. 3. Apply the patch and the extproc filter will not send the local reply that is generated by Envoy to the extproc server for processing. 4. Apply the patch that the router will cancel the upstream requests when sending a local reply.

Impact Denial of service

Reporter Vasilios Syrakis Fernando Cainelli

Envoy is a cloud-native high-performance edge/middle/service proxy. Envoy will crash when the http async client is handling sendLocalReply under some circumstance, e.g., websocket upgrade, and requests mirroring. The http async client will crash during the sendLocalReply() in http async client, one reason is http async client is duplicating the status code, another one is the destroy of router is called at the destructor of the async stream, while the stream is deferred deleted at first. There will be problems that the stream decoder is destroyed but its reference is called in router.onDestroy(), causing segment fault. This will impact extauthz if the upgrade and connection header are allowed, and request mirrorring. This issue has been addressed in versions 1.31.2, 1.30.6, 1.29.9, and 1.28.7. Users are advised to upgrade. There are no known workarounds for this vulnerability.