CVE-2021-21284

MediumCVSS 6.8/10Last modified Jun 17, 2026

Description

In Docker before versions 9.03.15, 20.10.3 there is a vulnerability involving the --userns-remap option in which access to remapped root allows privilege escalation to real root. 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. Versions 20.10.3 and 19.03.15 contain patches that prevent privilege escalation from remapped user.

Metrics

CVSS 3.1 6.8/10CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N

Weakness enumeration

CWE-22

Affected software

Vendor	Product	Versions
moby	moby	< 19.03.15; >= 20.0.0, < 20.10.3

References

https://docs.docker.com/engine/release-notes/#20103Release Notes, Vendor Advisory
https://github.com/moby/moby/commit/64bd4485b3a66a597c02c95f5776395e540b2c7cPatch, Third Party Advisory
https://github.com/moby/moby/releases/tag/v19.03.15Release Notes, Third Party Advisory
https://github.com/moby/moby/releases/tag/v20.10.3Release Notes, Third Party Advisory
https://github.com/moby/moby/security/advisories/GHSA-7452-xqpj-6rpcThird Party Advisory
https://security.gentoo.org/glsa/202107-23Patch, Third Party Advisory
https://security.netapp.com/advisory/ntap-20210226-0005/Third Party Advisory
https://www.debian.org/security/2021/dsa-4865Third Party Advisory
https://docs.docker.com/engine/release-notes/#20103Release Notes, Vendor Advisory
https://github.com/moby/moby/commit/64bd4485b3a66a597c02c95f5776395e540b2c7cPatch, Third Party Advisory
https://github.com/moby/moby/releases/tag/v19.03.15Release Notes, Third Party Advisory
https://github.com/moby/moby/releases/tag/v20.10.3Release Notes, Third Party Advisory
https://github.com/moby/moby/security/advisories/GHSA-7452-xqpj-6rpcThird Party Advisory
https://security.gentoo.org/glsa/202107-23Patch, Third Party Advisory
https://security.netapp.com/advisory/ntap-20210226-0005/Third Party Advisory
https://www.debian.org/security/2021/dsa-4865Third Party Advisory

Timeline

Published: Feb 2, 2021
Last modified: Jun 17, 2026
NVD status: Modified

Related CVEs from 2021

CVE-2021-212856.5In Docker before versions 9.03.15, 20.10.3 there is a vulnerability in which pulling an intentionally malformed Docker image manifest crashe CVE-2021-212868.8AVideo Platform is an open-source Audio and Video platform. It is similar to a self-hosted YouTube. In AVideo Platform before version 10.2 t CVE-2021-212877.7MinIO is a High Performance Object Storage released under Apache License v2.0. In MinIO before version RELEASE.2021-01-30T00-20-58Z there is CVE-2021-212884.3CarrierWave is an open-source RubyGem which provides a simple and flexible way to upload files from Ruby applications. In CarrierWave before CVE-2021-212898.3Mechanize is an open-source ruby library that makes automated web interaction easy. In Mechanize from version 2.0.0 and before version 2.7.7 CVE-2021-21297.9Vulnerability in the Oracle VM VirtualBox product of Oracle Virtualization (component: Core). The supported version that is affected is Prio CVE-2021-212905.5Netty is an open-source, asynchronous event-driven network application framework for rapid development of maintainable high performance prot CVE-2021-212916.1OAuth2 Proxy is an open-source reverse proxy and static file server that provides authentication using Providers (Google, GitHub, and others CVE-2021-212926.3Traccar is an open source GPS tracking system. In Traccar before version 4.12 there is an unquoted Windows binary path vulnerability. Only W CVE-2021-212937.5blaze is a Scala library for building asynchronous pipelines, with a focus on network IO. All servers running blaze-core before version 0.14 CVE-2021-212947.5Http4s (http4s-blaze-server) is a minimal, idiomatic Scala interface for HTTP services. Http4s before versions 0.21.17, 0.22.0-M2, and 1.0.0 CVE-2021-212955.9Netty is an open-source, asynchronous event-driven network application framework for rapid development of maintainable high performance prot