GHSA-rg2x-37c3-w2rh CVE-2026-42306 GO-2026-5617
Docker: Race condition in docker cp allows bind mount redirection to host path
- Severity
- 7.2 / 10
- High · CVSS 3.1
- Exploit chance (EPSS)
- 0.10%
- Chance of exploitation in the next 30 days. Higher than 1.02% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition
- CWE-61 UNIX Symbolic Link (Symlink) Following
- Fix
2.0.0-beta.14- Upgrade github.com/moby/moby/v2 to this version or later
Description
Summary
A race condition during docker cp mount setup allows a malicious container to redirect a bind mount target to an arbitrary host path, potentially overwriting host files or causing denial of service.
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 is created inside the container root and then a bind mount is attached using the container-relative path resolved to an absolute host path.
Between mountpoint creation and the mount() syscall, a process running inside the container can replace the destination (or a parent path component) with a symlink pointing to an arbitrary location on the host. The mount() syscall follows the symlink, causing the volume to be bind-mounted onto an arbitrary host path instead of the intended container path.
Impact
A malicious container can redirect a volume bind mount to an arbitrary host path. The impact depends on the volume content and mount options:
- If the volume is writable, arbitrary host files at the redirected path could be overwritten with the volume's contents.
- If the volume is read-only, the host path is masked by the mount for the duration of the operation, causing denial of service.
- In all cases the mount is temporary (torn down after the
docker cpcompletes), but the effects of any writes persist.
Conditions for exploitation
- A container must have at least one volume mount.
- A process inside the container must be able to rapidly create and swap symlinks at the volume mount destination path.
- An operator must initiate a
docker cpinto that container, or call thePUT /containers/{id}/archiveorHEAD /containers/{id}/archiveAPI endpoints.
Not affected
- Containers that do not have volume mounts are not affected, as the race occurs during volume bind-mount setup.
Workarounds
- Only run containers from trusted images.
- Avoid using
docker cpwith untrusted running containers. - Use authorization plugins to restrict access to the archive API endpoints (
PUT /containers/{id}/archive,HEAD /containers/{id}/archive).
Affected versions
Go
| Package | Vulnerable | Fixed in |
|---|---|---|
| github.com/docker/docker | <= 28.5.2 |
No fix yet |
| github.com/docker/docker | all versions |
No fix yet |
| github.com/moby/moby | <= 28.5.2 |
No fix yet |
| github.com/moby/moby | all versions |
No fix yet |
| github.com/moby/moby/v2 | < 2.0.0-beta.14 |
2.0.0-beta.14 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
github.com/moby/moby/v2 Go → 2.0.0-beta.14
- go
go get github.com/moby/moby/v2@v2.0.0-beta.14 && go mod tidy
Severity breakdown
CVSS 3.1 7.2
CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:N/I:H/A:H
- Attack vector
- Local
- Attack complexity
- High
- Privileges required
- Low
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- None
- Integrity
- High
- Availability
- High
Weakness
CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition
The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.
How to prevent it
- Implementation: The most basic advice for TOCTOU vulnerabilities is to not perform a check before the use. This does not resolve the underlying issue of the execution of a function on a resource whose state and identity cannot be assured, but it does help to limit the false sense of security given by the check.
- Implementation: When the file being altered is owned by the current user and group, set the effective gid and uid to that of the current user and group when executing this statement.
- Architecture and Design: Limit the interleaving of operations on files from multiple processes.
- Implementation, Architecture and Design: If you cannot perform operations atomically and you must share access to the resource between multiple processes or threads, then try to limit the amount of time (CPU cycles) between the check and use of the resource. This will not fix the problem, but it could make it more difficult for an attack to succeed.
- Implementation: Recheck the resource after the use call to verify that the action was taken appropriately.
- Architecture and Design: Ensure that some environmental locking mechanism can be used to protect resources effectively.
- Implementation: Ensure that locking occurs before the check, as opposed to afterwards, such that the resource, as checked, is the same as it is when in use.
CWE-61: UNIX Symbolic Link (Symlink) Following
The product, when opening a file or directory, does not sufficiently account for when the file is a symbolic link that resolves to a target outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files.
How to prevent it
- Implementation: Symbolic link attacks often occur when a program creates a tmp directory that stores files/links. Access to the directory should be restricted to the program as to prevent attackers from manipulating the files.
- Architecture and Design: Follow the principle of least privilege when assigning access rights to entities in a software system. Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.
References
Advisories
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-vp62-88p7-qqf5 Docker: Race condition in docker cp allows creation of arbitrary empty files on the host via symlink swap | Medium | Also affects github.com/docker/docker |
| GHSA-x86f-5xw2-fm2r Docker: `PUT /containers/{id}/archive` executes container binary on the host | High | Also affects github.com/docker/docker |
| GO-2026-4887 Moby has AuthZ plugin bypass when provided oversized request bodies | High | Also affects github.com/docker/docker |
| GHSA-pxq6-2prw-chj9 Moby has an Off-by-one error in its plugin privilege validation | High | Also affects github.com/docker/docker |
| GHSA-4vq8-7jfc-9cvp Moby firewalld reload removes bridge network isolation | Medium | Also affects github.com/docker/docker |
| GHSA-x4rx-4gw3-53p4 Moby firewalld reload makes published container ports accessible from remote hosts | Medium | Also affects github.com/docker/docker |
| GHSA-v23v-6jw2-98fq Authz zero length regression | Critical | Also affects github.com/docker/docker |
| GHSA-xmmx-7jpf-fx42 Moby (Docker Engine) is vulnerable to Ambiguous OCI manifest parsing | Low | Also affects github.com/docker/docker |
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