CVE-2021-21284: Github.com/moby/moby Moby Access To Remapped Root Vulnerability

MODERATE
Advisory Identifier: GHSA-7452-xqpj-6rpc
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CVSS 6.8
CWE-22
Published
Advisory Summary

CVE-2021-21284 is a MODERATE (CVSS 6.8) moby access to remapped root vulnerability (CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')) affecting Github.com/moby/moby libraries in the Go ecosystem. The issue involves moby access to remapped root allows privilege escalation to real root. Remediation is available by upgrading affected packages to version 19.3.15, 20.10.3.

CVE-2021-21284 at a Glance

CVE Identifier CVE-2021-21284
GHSA Identifier GHSA-7452-xqpj-6rpc
Severity MODERATE
CVSS v3.1 Base Score 6.8
CWE Classification CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Affected Product Github.com/moby/moby
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 6.8

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

Attack Vector Adjacent (AV:A)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Changed (S:C)
Confidentiality None (C:N)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2021-21284

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: 19.3.15 
Upgrade github.com/moby/moby to 19.3.15
github.com/moby/moby fixed: 20.10.3 
Upgrade github.com/moby/moby to 20.10.3
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-2021-21284, 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 19.3.15), 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-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'), where the product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. 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 When using `--userns-remap`, if the root user in the remapped namespace has access to the host filesystem they can modify files under `/var/lib/docker/<remapping>` that cause writing files with extended privileges. ### Patches Versions 20.10.3 and 19.03.15 contain patches that prevent privilege escalation from remapped user. ### Credits Maintainers would like to thank Alex Chapman for discovering the vulnerability; @awprice, @nathanburrell, @raulgomis, @chris-walz, @erin-jensby, @bassmatt, @mark-adams, @dbaxa for working on it and Zac Ellis for responsibly disclosing it to security@docker.com

CVE-2021-21284 Affected Github.com/moby/moby Versions

2 component(s)
Fixed Versions:
19.3.1520.10.3
Product / Package Ecosystem Affected Versions Fixed Version
github.com/moby/moby
golang/github.com/moby/moby
Go
< 19.3.15
19.3.15
github.com/moby/moby
golang/github.com/moby/moby
Go
≥ 20.10.0-beta1
< 20.10.3
20.10.3

References

GitHub Advisory / Wiki ADVISORY
https://github.com/moby/moby/security/advisories/GHSA-7452-xqpj-6rpc
NVD — CVE-2021-21284 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-21284
Security Fix Commit FIX COMMIT
https://github.com/moby/moby/commit/64bd4485b3a66a597c02c95f5776395e540b2c7c
docs.docker.com/engine/release-note... WEB
https://docs.docker.com/engine/release-notes/#20103
Github.com/moby/moby Release RELEASE
https://github.com/moby/moby/releases/tag/v19.03.15
Github.com/moby/moby Release RELEASE
https://github.com/moby/moby/releases/tag/v20.10.3
Github.com/moby/moby Security Information SECURITY
https://security.gentoo.org/glsa/202107-23
Github.com/moby/moby Security Information SECURITY
https://security.netapp.com/advisory/ntap-20210226-0005
Github.com/moby/moby Security Information SECURITY
https://www.debian.org/security/2021/dsa-4865

Frequently Asked Questions

What is CVE-2021-21284?
CVE-2021-21284 is a security vulnerability in Github.com/moby/moby involving moby Access to remapped root allows privilege escalation to real root under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal').
Which Github.com/moby/moby versions are affected?
Affected versions include releases prior to 19.3.15, 20.10.3 across affected packages: github.com/moby/moby.
What version fixes CVE-2021-21284?
Upgrading to 19.3.15, 20.10.3 (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 19.3.15, 20.10.3. Upgrade your dependency to 19.3.15, 20.10.3 or later.
What is the CVSS score of CVE-2021-21284?
CVE-2021-21284 has a CVSS v3.1 base score of 6.8 (MODERATE) with vector string CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N.
What CWE is associated with CVE-2021-21284?
CVE-2021-21284 is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') (The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.).
How can I check Go dependencies for CVE-2021-21284?
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
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-7452-xqpj-6rpc",
  "modified" : "2024-06-10T18:39:17Z",
  "published" : "2024-01-31T23:14:25Z",
  "aliases" : [ "CVE-2021-21284" ],
  "summary" : "moby Access to remapped root allows privilege escalation to real root",
  "details" : "### Impact\n\nWhen using `--userns-remap`, if the root user in the remapped namespace has access to the host filesystem they can modify files under `/var/lib/docker/<remapping>` that cause writing files with extended privileges.\n\n### Patches\n\nVersions 20.10.3 and 19.03.15 contain patches that prevent privilege escalation from remapped user.\n\n### Credits\n\nMaintainers would like to thank Alex Chapman for discovering the vulnerability; @awprice, @nathanburrell, @raulgomis, @chris-walz, @erin-jensby, @bassmatt, @mark-adams, @dbaxa for working on it and Zac Ellis for responsibly disclosing it to security@docker.com",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/moby/moby"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "19.3.15"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/moby/moby"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "20.10.0-beta1"
      }, {
        "fixed" : "20.10.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/moby/moby/security/advisories/GHSA-7452-xqpj-6rpc"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-21284"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/moby/moby/commit/64bd4485b3a66a597c02c95f5776395e540b2c7c"
  }, {
    "type" : "WEB",
    "url" : "https://docs.docker.com/engine/release-notes/#20103"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/moby/moby/releases/tag/v19.03.15"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/moby/moby/releases/tag/v20.10.3"
  }, {
    "type" : "WEB",
    "url" : "https://security.gentoo.org/glsa/202107-23"
  }, {
    "type" : "WEB",
    "url" : "https://security.netapp.com/advisory/ntap-20210226-0005"
  }, {
    "type" : "WEB",
    "url" : "https://www.debian.org/security/2021/dsa-4865"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-01-31T23:14:25Z",
    "nvd_published_at" : "2021-02-02T18:15:00Z"
  }
}