Envoy is a high-performance edge/middle/service proxy. External authentication can be bypassed by downstream connections. Downstream clients can force invalid gRPC requests to be sent to ext_authz, circumventing ext_authz checks when failure_mode_allow is set to true. This issue has been addressed in released 1.29.1, 1.28.1, 1.27.3, and 1.26.7. Users are advised to upgrade. There are no known workarounds for this vulnerability.
https://github.com/envoyproxy/envoy/security/advisories/GHSA-gq3v-vvhj-96j6
https://github.com/envoyproxy/envoy/security/advisories/GHSA-gq3v-vvhj-96j6
https://github.com/envoyproxy/envoy/commit/29989f6cc8bfd8cd2ffcb7c42711eb02c7a5168a
https://github.com/envoyproxy/envoy/commit/29989f6cc8bfd8cd2ffcb7c42711eb02c7a5168a