---
id: CVE-2021-21284
aliases:
  - GHSA-7452-xqpj-6rpc
title: moby Access to remapped root allows privilege escalation to real root
summary: moby Access to remapped root allows privilege escalation to real root
severity: medium
cvss: 6.8
cvssVector: 'CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N'
vendor: moby
product: github.com/moby/moby
ecosystem: go
affected:
  - github.com/moby/moby < 19.3.15
  - 'github.com/moby/moby >= 20.10.0-beta1, < 20.10.3'
patched:
  - github.com/moby/moby 19.3.15
  - github.com/moby/moby 20.10.3
published: '2024-01-31'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T03:50:09.391693398Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-7452-xqpj-6rpc'
references:
  - url: 'https://github.com/moby/moby/security/advisories/GHSA-7452-xqpj-6rpc'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2021-21284'
  - url: >-
      https://github.com/moby/moby/commit/64bd4485b3a66a597c02c95f5776395e540b2c7c
  - url: 'https://docs.docker.com/engine/release-notes/#20103'
  - url: 'https://github.com/moby/moby/releases/tag/v19.03.15'
  - url: 'https://github.com/moby/moby/releases/tag/v20.10.3'
  - url: 'https://security.gentoo.org/glsa/202107-23'
  - url: 'https://security.netapp.com/advisory/ntap-20210226-0005'
  - url: 'https://www.debian.org/security/2021/dsa-4865'
tags:
  - osv
  - go
epss: 0.01065
epssPercentile: 0.63233
ingestedAt: '2026-07-09T18:56:36.027Z'
---

## Overview

### 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

## Affected packages

- `github.com/moby/moby < 19.3.15`
- `github.com/moby/moby >= 20.10.0-beta1, < 20.10.3`

## Remediation

Upgrade to a patched release:

- `github.com/moby/moby 19.3.15`
- `github.com/moby/moby 20.10.3`