What’s Vulnerable › Vulnerabilities

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

• Severity: medium (CVSS 6.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-10-04 · updated 2026-06-17
• Weakness: CWE-281

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.

Affected products

• Fedoraproject Fedora: 34, 35
• Docker Engine: before 20.10.9 — fixed in 20.10.9

How to fix

Upgrade to a fixed version: Docker Engine 20.10.9. Check the vendor advisory for mitigations.

References

• https://cert-portal.siemens.com/productcert/pdf/ssa-222547.pdf
• https://github.com/moby/moby/commit/f0ab919f518c47240ea0e72d0999576bb8008e64
• https://github.com/moby/moby/security/advisories/GHSA-3fwx-pjgw-3558
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/B5Q6G6I4W5COQE25QMC7FJY3I3PAYFBB/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZNFADTCHHYWVM6W4NJ6CB4FNFM2VMBIB/
• https://cert-portal.siemens.com/productcert/pdf/ssa-222547.pdf
• https://github.com/moby/moby/commit/f0ab919f518c47240ea0e72d0999576bb8008e64
• https://github.com/moby/moby/security/advisories/GHSA-3fwx-pjgw-3558
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/B5Q6G6I4W5COQE25QMC7FJY3I3PAYFBB/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZNFADTCHHYWVM6W4NJ6CB4FNFM2VMBIB/

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