CVE-2021-41091: Insufficiently restricted permissions on data directory in Docker Engine

Vulnerability summary

CVE-2021-41091 is a medium (CVSS 6.3) Improper Preservation of Permissions vulnerability in fedoraproject fedora. EPSS estimates a 2.85% chance of exploitation in the next 30 days, higher than 86.7% of scored vulnerabilities.

Timeline

1. 04-10-2021
   PublishedVulnerability first disclosed.
2. 04-08-2024
   Last modifiedVulnerability information updated.

Description

Moby is an open-source project created by Docker to enable software containerization. A bug was found in Moby (Docker Engine) where the data directory (typically `/var/lib/docker`) contained subdirectories with insufficiently restricted permissions, allowing otherwise unprivileged Linux users to traverse directory contents and execute programs. When containers included executable programs with extended permission bits (such as `setuid`), unprivileged Linux users could discover and execute those programs. When the UID of an unprivileged Linux user on the host collided with the file owner or group inside a container, the unprivileged Linux user on the host could discover, read, and modify those files. This bug has been fixed in Moby (Docker Engine) 20.10.9. Users should update to this version as soon as possible. Running containers should be stopped and restarted for the permissions to be fixed. For users unable to upgrade limit access to the host to trusted users. Limit access to host volumes to trusted containers.

• CWE-281Improper Preservation of PermissionsThe product does not preserve permissions or incorrectly preserves permissions when copying, restoring, or sharing objects, which can cause them to have less restrictive permissions than intended.
• CWE-732Incorrect Permission Assignment for Critical ResourceThe product specifies permissions for a security-critical resource in a way that allows that resource to be read or modified by unintended actors.