Authentication bypass using an empty token in capsule-proxy

Vulnerability Description

capsule-proxy is a reverse proxy for the capsule operator project. Affected versions are subject to a privilege escalation vulnerability which is based on a missing check if the user is authenticated based on the `TokenReview` result. All the clusters running with the `anonymous-auth` Kubernetes API Server setting disable (set to `false`) are affected since it would be possible to bypass the token review mechanism, interacting with the upper Kubernetes API Server. This privilege escalation cannot be exploited if you're relying only on client certificates (SSL/TLS). This vulnerability has been addressed in version 0.4.6. Users are advised to upgrade.

References

• https://github.com/projectcapsule/capsule-proxy/security/advisories/GHSA-fpvw-6m5v-hqfp
• https://github.com/projectcapsule/capsule-proxy/commit/472404f7006a4152e4eec76dee07324dd1e6e823