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GHSA-2mm7-x5h6-5pvq
No affected components available
Impact
A bug was found in Moby (Docker Engine) where containers were incorrectly started with non-empty inheritable Linux process capabilities, creating an atypical Linux environment and enabling programs with inheritable file capabilities to elevate those capabilities to the permitted set during execve(2). Normally, when executable programs have specified permitted file capabilities, otherwise unprivileged users and processes can execute those programs and gain the specified file capabilities up to the bounding set. Due to this bug, containers which included executable programs with inheritable file capabilities allowed otherwise unprivileged users and processes to additionally gain these inheritable file capabilities up to the container's bounding set. Containers which use Linux users and groups to perform privilege separation inside the container are most directly impacted.
This bug did not affect the container security sandbox as the inheritable set never contained more capabilities than were included in the container's bounding set.
Patches
This bug has been fixed in Moby (Docker Engine) 20.10.14. Users should update to this version as soon as possible. Running containers should be stopped, deleted, and recreated for the inheritable capabilities to be reset.
This fix changes Moby (Docker Engine) behavior such that containers are started with a more typical Linux environment. Refer to capabilities(7) for a description of how capabilities work. Note that permitted file capabilities continue to allow for privileges to be raised up to the container's bounding set and that processes may add capabilities to their own inheritable set up to the container's bounding set per the rules described in the manual page. In all cases the container's bounding set provides an upper bound on the capabilities that can be assumed and provides for the container security sandbox.
Workarounds
The entrypoint of a container can be modified to use a utility like capsh(1) to drop inheritable capabilities prior to the primary process starting.
Credits
The Moby project would like to thank Andrew G. Morgan for responsibly disclosing this issue in accordance with the Moby security policy.
For more information
If you have any questions or comments about this advisory:
- Open an issue
- Email us at security@docker.com if you think you’ve found a security bug
The vulnerability requires local access to the device to be exploited. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data. There is a low impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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