Moby: Race condition in docker cp allows creation of arbitrary empty files on the host via symlink swap

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Moby: Race condition in docker cp allows creation of arbitrary empty files on the host via symlink swap

Moby is an open source container framework. In Docker Engine prior to version 29.5.1, Docker Daemon versions 28.5.2 and prior, and Moby Daemon prior to version 2.0.0-beta.14, a race condition during docker cp mount setup allows a malicious container to create empty files or directories at arbitrary absolute paths on the host filesystem. This issue has been patched in Docker Engine version 29.5.1 and Moby Daemon version 2.0.0-beta.14.

Source published

12 Jun 2026 18:08:43 UTC

Source modified

12 Jun 2026 20:01:58 UTC

Saved here

23 Oct 2026 15:48:27 UTC

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CVSS 3.1 · 6.1 CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:N/I:L/A:H

Moby is an open source container framework. In Docker Engine prior to version 29.5.1, Docker Daemon versions 28.5.2 and prior, and Moby Daemon prior to version 2.0.0-beta.14, a race condition during docker cp mount setup allows a malicious …

Moby is an open source container framework. In Docker Engine prior to version 29.5.1, Docker Daemon versions 28.5.2 and prior, and Moby Daemon prior to version 2.0.0-beta.14, a race condition during docker cp mount setup allows a malicious container to create empty files or directories at arbitrary absolute paths on the host filesystem. This issue has been patched in Docker Engine version 29.5.1 and Moby Daemon version 2.0.0-beta.14.

Source published

Jun 12, 2026, 6:08:43 PM (timezone not stated)

Source modified

Jun 12, 2026, 8:01:58 PM (timezone not stated)

Saved here

15 Nov 2026 16:45:27 UTC

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ENISA EUVD · source terms and attribution apply

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Source: euvd · ENISA EUVD · source terms and attribution apply. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

EUVD CVSS 3.1 · 6.1 CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:N/I:L/A:H

Moby is an open source container framework. In Docker Engine prior to version 29.5.1, Docker Daemon versions 28.5.2 and prior, and Moby Daemon prior to version 2.0.0-beta.14, a race condition during docker cp mount setup allows a malicious …

Moby is an open source container framework. In Docker Engine prior to version 29.5.1, Docker Daemon versions 28.5.2 and prior, and Moby Daemon prior to version 2.0.0-beta.14, a race condition during docker cp mount setup allows a malicious container to create empty files or directories at arbitrary absolute paths on the host filesystem. This issue has been patched in Docker Engine version 29.5.1 and Moby Daemon version 2.0.0-beta.14.

Source published

12 Jun 2026 19:16:26 UTC

Source modified

17 Jun 2026 10:46:51 UTC

Saved here

25 Oct 2026 09:17:41 UTC

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Source: nvd · NIST NVD usage terms; underlying source attribution retained. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

CVSS 3.1 · [email protected] · Secondary · 6.1 CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:N/I:L/A:H

Docker: Race condition in docker cp allows creation of arbitrary empty files on the host via symlink swap

## Summary A race condition during `docker cp` mount setup allows a malicious container to create empty files or directories at arbitrary absolute paths on the host filesystem. This advisory covers the race during mountpoint creation. The related race during the subsequent mount syscall is tracked in GHSA-rg2x-37c3-w2rh ## Details When copying files into a container, the daemon sets up a temporary filesystem view by bind-mounting volumes into a private mount namespace. During this setup, the mount destination path is first resolved within the container's root filesystem using `GetResourcePath`, and then used to create the mountpoint (file or directory) if it does not already exist via `createIfNotExists`. Between path resolution and mountpoint creation, a process running inside the container can swap a path component for a symlink pointing to an arbitrary location on the host. Because `createIfNotExists` operates on the already-resolved absolute path using standard `os.MkdirAll` and `os.OpenFile` — which follow symlinks in intermediate path components — the symlink is followed and the file or directory is created outside the container root filesystem, as root. ## Impact A malicious container can create empty files or directories at arbitrary absolute paths on the host filesystem, running as root. This enables persistent denial of service — for example: - Converting `/etc/docker/daemon.json` into a directory prevents the daemon from restarting - Creating `/etc/nologin` prevents user logins - Overwriting critical system paths with empty files can break host services The container does not gain read or write access to existing host files — only the ability to create new empty files or directories at chosen paths. ### Conditions for exploitation - A container must be running with a process that can rapidly create and swap symlinks at a volume mount destination path. - An operator must initiate a `docker cp` into that container, or call the `PUT /containers/{id}/archive` or `HEAD /containers/{id}/archive` API endpoints. ### Not affected - Containers that do not have volume mounts are not affected, as the race occurs during volume bind-mount setup. ## Patches Mountpoint creation is now scoped to the container root using `os.Root` (Go 1.24+), which refuses to follow symlinks that escape the opened root directory. All filesystem operations in `createIfNotExists` (`MkdirAll`, `OpenFile`) are performed through the `os.Root` handle, so even if a symlink swap occurs after path resolution, the creation stays confined to the container root. ## Workarounds - Only run containers from trusted images. - Avoid using `docker cp` with untrusted running containers. - Use authorization plugins to restrict access to the archive API endpoints (`PUT /containers/{id}/archive`, `HEAD /containers/{id}/archive`).

Source published

18 May 2026 17:52:55 UTC

Source modified

10 Sep 2026 03:51:07 UTC

Saved here

24 Oct 2026 13:19:41 UTC

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GitHub Advisory Database · CC-BY-4.0

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CVSS_V3 · CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:N/I:L/A:H

Publisher rating · MODERATE

Race condition in 'docker cp' in github.com/docker/docker allows creation of arbitrary files

A race condition in the Docker daemon allows an attacker to create arbitrary empty files on the host system during a "docker cp" operation by swapping a destination path with a symbolic link. The affected code is in the daemon package, specifically the openContainerFS and createIfNotExists methods. This is daemon-owned, Linux-specific code and is not intended for external use as a Go library.

Source published

25 Jun 2026 22:34:38 UTC

Source modified

11 Aug 2026 23:45:11 UTC

Saved here

24 Oct 2026 13:19:41 UTC

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OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

Source: osv · OSV · upstream source license applies. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.