What is CVE-2021-41091?

CVE-2021-41091 is a medium-severity vulnerability in Moby, classified under Improper Preservation of Permissions. CVSS score: 6.3/10. Published 2021-10-04.

How severe is CVE-2021-41091?

Medium severity. CVSS v3 base score is 6.3 out of 10.

Is CVE-2021-41091 known to be exploited?

11 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Vulnerability in Moby

CVE-2021-41091

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.

EPSS: 0.028 (86.0th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.3 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L.

Affected products

Moby — versions < 20.10.9
Mobyproject Moby
Fedoraproject Fedora — versions 34, 35

Weakness classification (CWE)

Public proof-of-concept exploits

References

security-advisories@github.com (x_refsource_CONFIRM, Third Party Advisory)
security-advisories@github.com (Patch, Third Party Advisory, x_refsource_MISC)
security-advisories@github.com (x_refsource_FEDORA, vendor-advisory)
security-advisories@github.com (x_refsource_FEDORA, vendor-advisory)
security-advisories@github.com (x_refsource_CONFIRM)

Frequently asked questions

What is CVE-2021-41091?: CVE-2021-41091 is a medium-severity vulnerability in Moby, classified under Improper Preservation of Permissions. CVSS score: 6.3/10. Published 2021-10-04.
How severe is CVE-2021-41091?: Medium severity. CVSS v3 base score is 6.3 out of 10.
Is CVE-2021-41091 known to be exploited?: 11 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.