GHSA-RG2X-37C3-W2RH
Vulnerability from github – Published: 2026-05-18 17:53 – Updated: 2026-05-18 17:53Summary
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": [
{
"package": {
"ecosystem": "Go",
"name": "github.com/docker/docker"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"last_affected": "28.5.2"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Go",
"name": "github.com/moby/moby/v2"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.0.0-beta.14"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Go",
"name": "github.com/moby/moby"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"last_affected": "28.5.2"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-42306"
],
"database_specific": {
"cwe_ids": [
"CWE-367",
"CWE-61"
],
"github_reviewed": true,
"github_reviewed_at": "2026-05-18T17:53:08Z",
"nvd_published_at": null,
"severity": "HIGH"
},
"details": "## Summary\n\nA 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.\n\n## Details\n\nWhen 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.\n\nBetween 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.\n\n## Impact\n\nA malicious container can redirect a volume bind mount to an arbitrary host path. The impact depends on the volume content and mount options:\n\n- If the volume is writable, arbitrary host files at the redirected path could be overwritten with the volume\u0027s contents.\n- If the volume is read-only, the host path is masked by the mount for the duration of the operation, causing denial of service.\n- In all cases the mount is temporary (torn down after the `docker cp` completes), but the effects of any writes persist.\n\n### Conditions for exploitation\n\n- A container must have at least one volume mount.\n- A process inside the container must be able to rapidly create and swap symlinks at the volume mount destination path.\n- An operator must initiate a `docker cp` into that container, or call the `PUT /containers/{id}/archive` or `HEAD /containers/{id}/archive` API endpoints.\n\n### Not affected\n\n- Containers that do not have volume mounts are not affected, as the race occurs during volume bind-mount setup.\n\n## Workarounds\n\n- Only run containers from trusted images.\n- Avoid using `docker cp` with untrusted running containers.\n- Use authorization plugins to restrict access to the archive API endpoints (`PUT /containers/{id}/archive`, `HEAD /containers/{id}/archive`).",
"id": "GHSA-rg2x-37c3-w2rh",
"modified": "2026-05-18T17:53:08Z",
"published": "2026-05-18T17:53:08Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/moby/moby/security/advisories/GHSA-rg2x-37c3-w2rh"
},
{
"type": "PACKAGE",
"url": "https://github.com/moby/moby"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:N/I:H/A:H",
"type": "CVSS_V3"
}
],
"summary": "Docker: Race condition in docker cp allows bind mount redirection to host path"
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.