CVE-2021-21284

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.

• CWE-22
• CWE-22

• 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

Published

Feb 2, 2021

Last Modified

Jun 17, 2026

Status

Modified

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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