CVSS score 8.6 (High), Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Envoy transitions a H/2 connection to the CLOSED state when it receives a GOAWAY frame without any streams outstanding. The connection state is transitioned to DRAINING when it receives a SETTING frame with the SETTINGS_MAX_CONCURRENT_STREAMS parameter set to 0. Receiving these two frames in the same I/O event results in abnormal termination of the Envoy process due to invalid state transition from CLOSED to DRAINING.

Impact

Denial of Service in the presence of untrusted upstream servers.

Attack Vector

A sequence of H/2 frames delivered by an untrusted upstream server.

Patches

Envoy versions 1.19.1, 1.18.4 contain fixes to stop processing of pending H/2 frames after connection transition to the CLOSED state.

Workarounds

None

Credits

Chaoqin Li (chaoqinli@google.com)

References

https://blog.envoyproxy.io
https://github.com/envoyproxy/envoy/releases

For more information

If you have any questions or comments about this advisory:

Open an issue in Envoy repo
Email us at envoy-security