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Vulnerability record · CVE-2021-21284 · published 2 February 2021

CVE-2021-21284: Docker path traversal vulnerability

Docker · Docker

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.

6.8 CVSS 3.1 Medium EPSS 1.1% · top 36.7% CWE-22 · Path traversal
6.8CVSS 3.1 base score, v2 2.7
1.1%EPSS exploitation probability, 30 days
NoNot in CISA KEV
3Affected product versions listed by NVD
16References
17 Jun 2026Last modified by NVD

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.

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

Affected products

3 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://docs.docker.com/engine/release-notes/#20103 Release NotesVendor Advisory
https://github.com/moby/moby/commit/64bd4485b3a66a597c02c95f5776395e540b2c7c PatchThird Party Advisory
https://github.com/moby/moby/releases/tag/v19.03.15 Release NotesThird Party Advisory
https://github.com/moby/moby/releases/tag/v20.10.3 Release NotesThird Party Advisory
https://github.com/moby/moby/security/advisories/GHSA-7452-xqpj-6rpc Third Party Advisory
https://security.gentoo.org/glsa/202107-23 PatchThird Party Advisory
https://security.netapp.com/advisory/ntap-20210226-0005/ Third Party Advisory
https://www.debian.org/security/2021/dsa-4865 Third Party Advisory
https://docs.docker.com/engine/release-notes/#20103 Release NotesVendor Advisory
https://github.com/moby/moby/commit/64bd4485b3a66a597c02c95f5776395e540b2c7c PatchThird Party Advisory
https://github.com/moby/moby/releases/tag/v19.03.15 Release NotesThird Party Advisory
https://github.com/moby/moby/releases/tag/v20.10.3 Release NotesThird Party Advisory
https://github.com/moby/moby/security/advisories/GHSA-7452-xqpj-6rpc Third Party Advisory
https://security.gentoo.org/glsa/202107-23 PatchThird Party Advisory
https://security.netapp.com/advisory/ntap-20210226-0005/ Third Party Advisory
https://www.debian.org/security/2021/dsa-4865 Third Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2021-21284), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.