Traefik may display authorization header in the debug logs

Impact

There is a potential vulnerability in Traefik displaying the Authorization header in its debug logs.

Traefik uses oxy to provide the following features:

• Round Robin: https://doc.traefik.io/traefik/routing/services/#weighted-round-robin-service
• Buffering: https://doc.traefik.io/traefik/middlewares/http/buffering/
• Circuit Breaker: https://doc.traefik.io/traefik/middlewares/http/circuitbreaker/
• In-Flight Requests: https://doc.traefik.io/traefik/middlewares/http/inflightreq/

In such cases, if the log level is set to DEBUG, the credentials provided using the Authorization header are displayed in the debug logs:

level=debug msg="vulcand/oxy/roundrobin/rr: completed ServeHttp on request" Request="{\\"Method\\":\\"POST\\",\\"URL\\":{\\"Scheme\\":\\"\\",\\"Opaque\\":\\"\\",\\"User\\":null,\\"Host\\":\\"\\",\\"Path\\":\\"/<redacted>/<redacted>\\",\\"RawPath\\":\\"\\",\\"ForceQuery\\":false,\\"RawQuery\\":\\"\\",\\"Fragment\\":\\"\\",\\"RawFragment\\":\\"\\"},\\"Proto\\":\\"HTTP/2.0\\",\\"ProtoMajor\\":2,\\"ProtoMinor\\":0,\\"Header\\":{\\"Authorization\\":[\\"Bearer <token value was here>\\"],\\"Content-Type\\":[\\"application/grpc\\"],\\"Grpc-Accept-Encoding\\":[\\"gzip\\"],\\"Grpc-Timeout\\":[\\"29999886u\\"],\\"Te\\":[\\"trailers\\"],\\"User-Agent\\":[\\"<redacted>\\"],<remainder of log message removed>

Patches

https://github.com/traefik/traefik/pull/9574
https://github.com/traefik/traefik/releases/tag/v2.9.6

Workarounds

Set the log level to INFO, WARN, or ERROR.

For more information

If you have any questions or comments about this advisory, please open an issue.