docker cp allows unexpected chmod of host files in Moby Docker Engine

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2021-41089: 0.29% estimated exploitation activity in the next 30 days; percentile 21.65 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact A bug was found in Moby (Docker Engine) where attempting to copy files using docker cp into a specially-crafted container can result in Unix file permission changes for existing files in the host’s filesystem, widening access to others. This bug does not directly allow files to be read, modified, or executed without an additional cooperating process. Patches This bug has been fixed in Moby (Docker Engine) 20.10.9. Users should update to this version as soon as possible. Running containers do not need to be restarted. Workarounds Ensure you only run trusted containers. Credits The Moby project would like to thank Lei Wang and Ruizhi Xiao for responsibly disclosing this issue in accordance with the Moby security policy. For more information If you have any questions or comments about this advisory: Open an issue Email us at security@docker.com if you think you’ve found a security bug

Published by the source

10 Jun 2024, 18:38 UTC

Last modified by the source

3 Jul 2024, 20:27 UTC

Source last checked

26 Oct 2026, 15:04 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-v994-f8vw-g7j4

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2021-41089

Advisory: `docker cp` allows unexpected chmod of host files in Moby Docker Engine
IDs: CVE-2021-41089, GHSA-v994-f8vw-g7j4
Record: https://patchnext.com/advisories/cve-2021-41089 (revision 1, source checked 26 Oct 2026, 15:04 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 2.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/docker/docker 20.10.9. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/docker/docker: affected < 20.10.9; fixed in 20.10.9

## Suggested inspection (read-only)
- Go github.com/docker/docker: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/docker/docker.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-v994-f8vw-g7j4 (GitHub-reviewed advisory GHSA-v994-f8vw-g7j4 lists affected ranges: Go github.com/docker/docker >=0 <20.10.9)

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