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CVE-2021-21284

6.8 · MEDIUM

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.

Published Feb 2, 2021CWE-22EPSS 1.06%

Overview

CVE-2021-21284 is a medium-severity vulnerability. It was published on February 2, 2021 and has a CVSS 3.1 base score of 6.8 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 6.8, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refdocs.docker.com/engine/release-notes/#20103GitHubgithub.com/moby/moby/commit/64bd4485b3a66a597c02c95f5776395e540b2c7cGitHubgithub.com/moby/moby/releases/tag/v19.03.15GitHubgithub.com/moby/moby/releases/tag/v20.10.3GitHubgithub.com/moby/moby/security/advisories/GHSA-7452-xqpj-6rpcRefsecurity.gentoo.org/glsa/202107-23Refsecurity.netapp.com/advisory/ntap-20210226-0005/Refwww.debian.org/security/2021/dsa-4865Refdocs.docker.com/engine/release-notes/#20103GitHubgithub.com/moby/moby/commit/64bd4485b3a66a597c02c95f5776395e540b2c7c

How CyberStrike helps

Frequently asked questions

What is CVE-2021-21284?

CVE-2021-21284 is a medium-severity vulnerability. It was published on February 2, 2021 and has a CVSS 3.1 base score of 6.8 (MEDIUM).

How severe is CVE-2021-21284?

This vulnerability has a CVSS 3.1 base score of 6.8, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2021-21284?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2021-21284?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2021-21284 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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