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

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.

Published: 2021-10-04 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-41091 is rated Moderate Risk (51.8/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 2.49%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-41091

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 4.75% 2.49% -2.25%
2 2026-04-10 5.58% 4.75% -0.83%
3 2026-03-11 — 5.58% —

Full EPSS history (28 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-41091

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.3 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 2.0 3.7 [email protected]
6.3 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 2.0 3.7 [email protected]
4.6 2.0 MEDIUM
AV:L/AC:L/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:L)
Requires local access to the target system.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 3.9 6.4 [email protected]

Weakness enumeration for CVE-2021-41091

GitHub Security Advisory for CVE-2021-41091

GHSA-3fwx-pjgw-3558 · Severity: medium · Ecosystem: go — Moby (Docker Engine) Insufficiently restricted permissions on data directory

OS Trackers for CVE-2021-41091

vendor priority summary link
alpine medium CVE-2021-41091: 1 source package rows (docker); 7 state rows across 7 repos (3.17-community, 3.18-community, 3.19-community, 3.20-community, 3.21-community, 3.22-community, edge-community); fixed 7, open 0. https://security.alpinelinux.org/vuln/CVE-2021-41091
debian not yet assigned CVE-2021-41091 not yet assigned priority: Debian including 1 source packages (docker.io), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-41091
gentoo low CVE-2021-41091: 1 GLSA(s) (202409-29), 1 atom(s) (app-containers/docker); latest impact low. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-41091
redhat medium — https://access.redhat.com/security/cve/CVE-2021-41091
suse medium CVE-2021-41091 severity moderate: SUSE including 55 source package names (2.0.2-4.2.20:runc-1.0.2-23.1, containerd-1.4.11-56.1, …), 1003 product×package rows across 325 product lines (Container rancher/elemental-teal-iso/5.4, Container rancher/elemental-teal-rt/5.4, … (325 product lines)): Fixed 1003. https://www.suse.com/security/cve/CVE-2021-41091/
ubuntu medium CVE-2021-41091 medium priority: Ubuntu including 1 source packages (docker.io), 9 status rows across 9 suites (bionic, focal, hirsute, impish, jammy, kinetic, trusty, upstream, xenial): released 6, DNE 1, ignored 1, not-affected 1. https://ubuntu.com/security/CVE-2021-41091

Affected software / configurations for CVE-2021-41091

Vendor Product Version Raw CPE
mobyproject moby < 20.10.9 cpe:2.3:a:mobyproject:moby:*:*:*:*:*:*:*:*
fedoraproject fedora 34 cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
fedoraproject fedora 35 cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*

References for CVE-2021-41091

cvelogic Threat Intelligence