CVE-2021-21284

Name: CVE-2021-21284
Creator: NVD / NIST
Published: 2021-02-02T18:15:11.827+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.8/10EPSS 1.06%

Last modified Jun 17, 2026

CVE-2021-21284 is a medium-severity vulnerability rated 6.8/10 on the CVSS scale. 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. EPSS estimates a 1.06% chance of exploitation in the next 30 days.

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

6.8/10

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

EPSS Probability

1.06%

60.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Docker	Docker	< 19.03.15
Docker	Docker	>= 20.0.0, < 20.10.3
Debian	Debian Linux	10.0
Netapp	E-Series Santricity Os Controller	>= 11.0.0, <= 11.60.3

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
Status: Modified

Frequently Asked Questions

What is CVE-2021-21284?

How severe is CVE-2021-21284?

CVE-2021-21284 has a CVSS score of 6.8/10 (MEDIUM severity). The EPSS model estimates a 1.06% probability of exploitation in the next 30 days.

How do I fix CVE-2021-21284?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-21284?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST