{"id":"CVE-2021-21284","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-21284","generatedAt":"2026-10-27T20:22:16.965Z","title":"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.","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.","published":"2021-02-02T18:15:12.000Z","lastModified":"2026-06-17T03:35:12.000Z","status":"Modified","sourceIdentifier":"security-advisories@github.com","cvss":{"version":"3.1","score":6.8,"severity":"MEDIUM","vector":"CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N"},"cwe":["CWE-22"],"affected":["docker/docker","debian/debian linux","netapp/e-series santricity os controller"],"epss":{"score":0.01065,"percentile":0.64455,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (1.06%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"https://docs.docker.com/engine/release-notes/#20103","tags":["Release Notes","Vendor Advisory"],"source":"security-advisories@github.com"},{"url":"https://github.com/moby/moby/commit/64bd4485b3a66a597c02c95f5776395e540b2c7c","tags":["Patch","Third Party Advisory"],"source":"security-advisories@github.com"},{"url":"https://github.com/moby/moby/releases/tag/v19.03.15","tags":["Release Notes","Third Party Advisory"],"source":"security-advisories@github.com"},{"url":"https://github.com/moby/moby/releases/tag/v20.10.3","tags":["Release Notes","Third Party Advisory"],"source":"security-advisories@github.com"},{"url":"https://github.com/moby/moby/security/advisories/GHSA-7452-xqpj-6rpc","tags":["Third Party Advisory"],"source":"security-advisories@github.com"},{"url":"https://security.gentoo.org/glsa/202107-23","tags":["Patch","Third Party Advisory"],"source":"security-advisories@github.com"},{"url":"https://security.netapp.com/advisory/ntap-20210226-0005/","tags":["Third Party Advisory"],"source":"security-advisories@github.com"},{"url":"https://www.debian.org/security/2021/dsa-4865","tags":["Third Party Advisory"],"source":"security-advisories@github.com"},{"url":"https://docs.docker.com/engine/release-notes/#20103","tags":["Release Notes","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/moby/moby/commit/64bd4485b3a66a597c02c95f5776395e540b2c7c","tags":["Patch","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/moby/moby/releases/tag/v19.03.15","tags":["Release Notes","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/moby/moby/releases/tag/v20.10.3","tags":["Release Notes","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/moby/moby/security/advisories/GHSA-7452-xqpj-6rpc","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://security.gentoo.org/glsa/202107-23","tags":["Patch","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://security.netapp.com/advisory/ntap-20210226-0005/","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.debian.org/security/2021/dsa-4865","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-21284","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}