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Vulnerability record · CVE-2021-41091 · published 4 October 2021

CVE-2021-41091: Mobyproject moby incorrect permission assignment vulnerability

Mobyproject · Moby

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.

6.3 CVSS 3.1 Medium EPSS 2.8% · top 13.8% CWE-281 · CWE-281CWE-732 · Incorrect permission assignment
6.3CVSS 3.1 base score, v2 4.6
2.8%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
10References
17 Jun 2026Last modified by NVD

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.

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://cert-portal.siemens.com/productcert/pdf/ssa-222547.pdf
https://github.com/moby/moby/commit/f0ab919f518c47240ea0e72d0999576bb8008e64 PatchThird Party Advisory
https://github.com/moby/moby/security/advisories/GHSA-3fwx-pjgw-3558 Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/B5Q6G6I4W5COQE25QMC7FJY
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZNFADTCHHYWVM6W4NJ6CB4F
https://cert-portal.siemens.com/productcert/pdf/ssa-222547.pdf
https://github.com/moby/moby/commit/f0ab919f518c47240ea0e72d0999576bb8008e64 PatchThird Party Advisory
https://github.com/moby/moby/security/advisories/GHSA-3fwx-pjgw-3558 Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/B5Q6G6I4W5COQE25QMC7FJY
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZNFADTCHHYWVM6W4NJ6CB4F

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Source: NIST National Vulnerability Database (record CVE-2021-41091), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.