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Servers and applications

CVE-2021-21284

Access to remapped root allows privilege escalation to real root

Severity
Medium 6.8
Published
2 Feb 2021
Last changed
17 Jun 2026
Added to UpHeron
21 Oct 2026
Fixed in
19.03.15, 20.10.3
Also known as
GHSA-7452-xqpj-6rpc
Sources
NVD, Project advisories (GitHub)

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.…

Affected software

SoftwareAffected versions
Docker EngineServers and applications · cpe:a:docker:docker
  • Every version before 19.03.15
  • From 20.0.0 before 20.10.3
Docker EngineServers and applications · github:moby/moby
  • Every version before 20.10.3

References

  • NVD https://nvd.nist.gov/vuln/detail/CVE-2021-21284
  • CVE.org https://www.cve.org/CVERecord?id=CVE-2021-21284
  • GitHub Advisory Database https://github.com/advisories/GHSA-7452-xqpj-6rpc
  • github.com https://github.com/moby/moby/security/advisories/GHSA-7452-xqpj-6rpc