CVE-2026-42306: Docker Race Condition Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-rg2x-37c3-w2rh",
  "modified" : "2026-06-12T21:59:32Z",
  "published" : "2026-05-18T17:53:08Z",
  "aliases" : [ "CVE-2026-42306" ],
  "summary" : "Docker: Race condition in docker cp allows bind mount redirection to host path",
  "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's 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`).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:N/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/docker/docker"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "28.5.2"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/moby/moby/v2"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.0.0-beta.14"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/moby/moby"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "28.5.2"
      } ]
    } ]
  } ],
  "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"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-367", "CWE-61" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-18T17:53:08Z",
    "nvd_published_at" : "2026-06-12T19:16:27Z"
  }
}