Docker supplementary group permissions not set up properly, allowing attackers to bypass primary group restrictionsGHSA-rc4r-wh2q-q6c4
MEDIUMFix: moby/moby@de7af81GHSA-rc4r-wh2q-q6c4 is a medium-severity (CVSS 5.3) CWE-863 vulnerability in github.com/docker/docker. A fix is available for github.com/docker/docker — see the affected versions and patch details below.
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-rc4r-wh2q-q6c4.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
github.com/docker/dockerReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
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
For more information
If you have any questions or comments about this advisory:
- Open an issue
- Email us at [email protected]
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/docker/docker | all versions | 20.10.18go get github.com/docker/docker@v20.10.18 |
Affected Products
fedorafedoraprojectmobymobyprojectDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/docker/docker, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/docker/docker to 20.10.18 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-rc4r-wh2q-q6c4 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
Frequently Asked Questions
Is GHSA-rc4r-wh2q-q6c4 in your dependencies?
Find it across Go, including transitive dependencies.