GHSA-rc4r-wh2q-q6c4

Docker supplementary group permissions not set up properly, allowing attackers to bypass primary group restrictions

Moby is an open-source project created by Docker to enable software containerization. A bug was found in Moby (Docker Engine) where supplementary groups are not set up properly. If an attacker has direct access to a container and manipulates their supplementary group access, they may be able to use supplementary group access to bypass primary group restrictions in some cases, potentially gaining access to sensitive information or gaining the ability to execute code in that container. This bug is fixed in Moby (Docker Engine) 20.10.18. Users should update to this version when it is available. Running containers should be stopped and restarted for the permissions to be fixed. For users unable to upgrade, this problem can be worked around by not using the `"USER $USERNAME"` Dockerfile instruction. Instead by calling `ENTRYPOINT ["su", "-", "user"]` the supplementary groups will be set up properly. Thanks to Steven Murdoch for reporting this issue. ---- ### Impact If an attacker has direct access to a container and manipulates their supplementary group access, they may be able to use supplementary group access to bypass primary group restrictions in some cases, potentially gaining access to sensitive information or gaining the ability to execute code in that container. ### Patches This bug is fixed in Moby (Docker Engine) 20.10.18. Users should update to this version when it is available. ### Workarounds This problem can be worked around by not using the `"USER $USERNAME"` Dockerfile instruction. Instead by calling `ENTRYPOINT ["su", "-", "user"]` the supplementary groups will be set up properly. ### References https://www.benthamsgaze.org/2022/08/22/vulnerability-in-linux-containers-investigation-and-mitigation/ ### For more information If you have any questions or comments about this advisory: * [Open an issue](https://github.com/moby/moby/issues/new) * Email us at [security@docker.com](mailto:security@docker.com)