Headline
CVE-2023-27487: Client may fake the header `x-envoy-original-path`
Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to versions 1.26.0, 1.25.3, 1.24.4, 1.23.6, and 1.22.9, the client may bypass JSON Web Token (JWT) checks and forge fake original paths. The header x-envoy-original-path should be an internal header, but Envoy does not remove this header from the request at the beginning of request processing when it is sent from an untrusted client. The faked header would then be used for trace logs and grpc logs, as well as used in the URL used for jwt_authn checks if the jwt_authn filter is used, and any other upstream use of the x-envoy-original-path header. Attackers may forge a trusted x-envoy-original-path header. Versions 1.26.0, 1.25.3, 1.24.4, 1.23.6, and 1.22.9 have patches for this issue.
Impact
Bypass JWT checks, forge fake original paths.
Affected components
Trace logs, gRPC logs, JWT filter.
Attack vector/s
The header x-envoy-original-path should be an internal header, but Envoy does not remove this header from the request at the beginning of request processing when it is sent from an untrusted client.
The faked header would then be used for trace logs and grpc logs, as well as used in the URL used for jwt_authn checks if the jwt_authn filter is used, and any other upstream use of the x-envoy-original-path header.
Description
Trusted x-envoy-original-path header can be forged by attackers
Example exploit or proof-of-concept
Client request:
$ curl -H “x-envoy-original-path: /fake” http://localhost:8080/real-path/
Access log, using the default log format:
[2023-02-28T19:26:53.660Z] “GET /fake HTTP/1.1” 200 - 0 3257 1 0 "-" “curl/7.82.0” “36174006-b793-4e40-8a38-a3d17a2a37a0” “localhost:8080” “172.18.98.50:8020”
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