CVE-2021-41091: Github.com/moby/moby Moby (Docker Engine) Insufficiently Restricted Vulnerability

MODERATE
Advisory Identifier: GHSA-3fwx-pjgw-3558
CVSS 5.9
CWE-732 CWE-281
Published
Advisory Summary

CVE-2021-41091 is a MODERATE (CVSS 5.9) moby (docker engine) insufficiently restricted vulnerability (CWE-732: Incorrect Permission Assignment for Critical Resource) affecting Github.com/moby/moby libraries in the Go ecosystem. The issue involves moby (docker engine) insufficiently restricted permissions on data directory. Remediation is available by upgrading affected packages to version 20.10.9.

CVE-2021-41091 at a Glance

CVE Identifier CVE-2021-41091
GHSA Identifier GHSA-3fwx-pjgw-3558
Severity MODERATE
CVSS v3.1 Base Score 5.9
CWE Classification CWE-732: Incorrect Permission Assignment for Critical Resource
Affected Product Github.com/moby/moby
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 5.9

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L).

Attack Vector Local (AV:L)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability Low (A:L)

How to Fix CVE-2021-41091

To remediate this vulnerability, upgrade all affected Github.com/moby/moby dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

github.com/moby/moby fixed: 20.10.9
Upgrade github.com/moby/moby to 20.10.9
github.com/docker/docker fixed: 20.10.9
Upgrade github.com/docker/docker to 20.10.9
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release:

inspect dependencies for github.com/moby/moby

How to Check if You Are Affected

To determine whether your application is affected by CVE-2021-41091, inspect your project dependencies for Github.com/moby/moby:

inspect dependencies for github.com/moby/moby

Analyze the terminal output to locate any version of Github.com/moby/moby in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 20.10.9), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-732: Incorrect Permission Assignment for Critical Resource, where the product specifies permissions for a security-critical resource in a way that allows that resource to be read or modified by unintended actors. In Github.com/moby/moby, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

## Impact A bug was found in Moby (Docker Engine) where the data directory (typically `/var/lib/docker`) contained subdirectories with insufficiently restricted permissions, allowing otherwise unprivileged Linux users to traverse directory contents and execute programs. When containers included executable programs with extended permission bits (such as `setuid`), unprivileged Linux users could discover and execute those programs. When the UID of an unprivileged Linux user on the host collided with the file owner or group inside a container, the unprivileged Linux user on the host could discover, read, and modify those files. ## Patches This bug has been fixed in Moby (Docker Engine) 20.10.9. Users should update to this version as soon as possible. Running containers should be stopped and restarted for the permissions to be fixed. ## Workarounds Limit access to the host to trusted users. Limit access to host volumes to trusted containers. ## Credits The Moby project would like to thank Joan Bruguera for responsibly disclosing this issue in accordance with the [Moby security policy](https://github.com/moby/moby/blob/master/SECURITY.md). ## For more information If you have any questions or comments about this advisory: * [Open an issue](https://github.com/moby/moby/issues/new) * Email us at security@docker.com if you think you’ve found a security bug

CVE-2021-41091 Affected Github.com/moby/moby Versions

2 component(s)
Fixed Versions:
20.10.9
Product / Package Ecosystem Affected Versions Fixed Version
github.com/moby/moby
Go
< 20.10.9
20.10.9
github.com/docker/docker
Go
< 20.10.9
20.10.9

References

Frequently Asked Questions

What is CVE-2021-41091?
CVE-2021-41091 is a security vulnerability in Github.com/moby/moby involving Moby (Docker Engine) Insufficiently restricted permissions on data directory under CWE-732: Incorrect Permission Assignment for Critical Resource.
Which Github.com/moby/moby versions are affected?
Affected versions include releases prior to 20.10.9 across affected packages: github.com/moby/moby, github.com/docker/docker.
What version fixes CVE-2021-41091?
Upgrading to 20.10.9 (or the latest patched release for your respective branch) resolves the vulnerability.
Is github.com/moby/moby affected?
Yes, github.com/moby/moby is affected in releases prior to 20.10.9. Upgrade your dependency to 20.10.9 or later.
Is github.com/docker/docker affected?
Yes, github.com/docker/docker is affected in releases prior to 20.10.9. Upgrade your dependency to 20.10.9 or later.
What is the CVSS score of CVE-2021-41091?
CVE-2021-41091 has a CVSS v3.1 base score of 5.9 (MODERATE) with vector string CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L.
What CWE is associated with CVE-2021-41091?
CVE-2021-41091 is classified under CWE-732: Incorrect Permission Assignment for Critical Resource (The product specifies permissions for a security-critical resource in a way that allows that resource to be read or modified by unintended actors.).
How can I check Go dependencies for CVE-2021-41091?
Run the dependency tree command: 'inspect dependencies for github.com/moby/moby'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-3fwx-pjgw-3558",
  "modified" : "2024-05-14T22:00:30Z",
  "published" : "2024-01-31T23:28:58Z",
  "aliases" : [ "CVE-2021-41091" ],
  "summary" : "Moby (Docker Engine) Insufficiently restricted permissions on data directory",
  "details" : "## Impact\n\nA bug was found in Moby (Docker Engine) where the data directory (typically `/var/lib/docker`) contained subdirectories with insufficiently restricted permissions, allowing otherwise unprivileged Linux users to traverse directory contents and execute programs.  When containers included executable programs with extended permission bits (such as `setuid`), unprivileged Linux users could discover and execute those programs.  When the UID of an unprivileged Linux user on the host collided with the file owner or group inside a container, the unprivileged Linux user on the host could discover, read, and modify those files.\n\n## Patches\n\nThis bug has been fixed in Moby (Docker Engine) 20.10.9.  Users should update to this version as soon as possible.  Running containers should be stopped and restarted for the permissions to be fixed.\n\n## Workarounds\n\nLimit access to the host to trusted users.  Limit access to host volumes to trusted containers.\n\n## Credits\n\nThe Moby project would like to thank Joan Bruguera for responsibly disclosing this issue in accordance with the [Moby security policy](https://github.com/moby/moby/blob/master/SECURITY.md).\n\n## For more information\n\nIf you have any questions or comments about this advisory:\n\n* [Open an issue](https://github.com/moby/moby/issues/new)\n* Email us at security@docker.com if you think you’ve found a security bug",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/moby/moby"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "20.10.9"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/docker/docker"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "20.10.9"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/moby/moby/security/advisories/GHSA-3fwx-pjgw-3558"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-41091"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/moby/moby/commit/f0ab919f518c47240ea0e72d0999576bb8008e64"
  }, {
    "type" : "WEB",
    "url" : "https://cert-portal.siemens.com/productcert/pdf/ssa-222547.pdf"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/moby/moby"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/B5Q6G6I4W5COQE25QMC7FJY3I3PAYFBB"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ZNFADTCHHYWVM6W4NJ6CB4FNFM2VMBIB"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-281", "CWE-732" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-01-31T23:28:58Z",
    "nvd_published_at" : "2021-10-04T21:15:00Z"
  }
}