GHSA-RG2X-37C3-W2RH

Vulnerability from github – Published: 2026-05-18 17:53 – Updated: 2026-06-12 21:59
VLAI
Summary
Docker: Race condition in docker cp allows bind mount redirection to host path
Details

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 cp completes), 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 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.

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).
Severity
7.2 (High)
CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:N/I:H/A:H
Show details on source website
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{
  "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": "2026-06-12T19:16:27Z",
    "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": "2026-06-12T21:59:32Z",
  "published": "2026-05-18T17:53:08Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/moby/moby/security/advisories/GHSA-rg2x-37c3-w2rh"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-42306"
    },
    {
      "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"
}



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