{"id":"ALPINE-CVE-2021-21284","details":"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/\u003cremapping\u003e\" that cause writing files with extended privileges. Versions 20.10.3 and 19.03.15 contain patches that prevent privilege escalation from remapped user.","modified":"2026-11-03T06:32:27.244635849Z","published":"2021-02-02T18:15:11.827Z","upstream":["CVE-2021-21284"],"references":[{"type":"ADVISORY","url":"https://security.alpinelinux.org/vuln/CVE-2021-21284"}],"affected":[{"package":{"name":"docker","ecosystem":"Alpine:v3.12","purl":"pkg:apk/alpine/docker?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"20.0.0"},{"fixed":"20.10.3-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-21284.json"}},{"package":{"name":"docker","ecosystem":"Alpine:v3.13","purl":"pkg:apk/alpine/docker?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"20.0.0"},{"fixed":"20.10.3-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-21284.json"}},{"package":{"name":"docker","ecosystem":"Alpine:v3.14","purl":"pkg:apk/alpine/docker?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"20.0.0"},{"fixed":"20.10.3-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-21284.json"}},{"package":{"name":"docker","ecosystem":"Alpine:v3.15","purl":"pkg:apk/alpine/docker?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"20.0.0"},{"fixed":"20.10.3-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-21284.json"}},{"package":{"name":"docker","ecosystem":"Alpine:v3.16","purl":"pkg:apk/alpine/docker?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"20.0.0"},{"fixed":"20.10.3-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-21284.json"}},{"package":{"name":"docker","ecosystem":"Alpine:v3.17","purl":"pkg:apk/alpine/docker?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"20.0.0"},{"fixed":"20.10.3-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-21284.json"}},{"package":{"name":"docker","ecosystem":"Alpine:v3.18","purl":"pkg:apk/alpine/docker?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"20.0.0"},{"fixed":"20.10.3-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-21284.json"}},{"package":{"name":"docker","ecosystem":"Alpine:v3.19","purl":"pkg:apk/alpine/docker?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"20.0.0"},{"fixed":"20.10.3-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-21284.json"}},{"package":{"name":"docker","ecosystem":"Alpine:v3.20","purl":"pkg:apk/alpine/docker?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"20.0.0"},{"fixed":"20.10.3-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-21284.json"}},{"package":{"name":"docker","ecosystem":"Alpine:v3.21","purl":"pkg:apk/alpine/docker?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"20.0.0"},{"fixed":"20.10.3-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-21284.json"}},{"package":{"name":"docker","ecosystem":"Alpine:v3.22","purl":"pkg:apk/alpine/docker?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"20.0.0"},{"fixed":"20.10.3-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-21284.json"}},{"package":{"name":"docker","ecosystem":"Alpine:v3.23","purl":"pkg:apk/alpine/docker?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"20.0.0"},{"fixed":"20.10.3-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-21284.json"}},{"package":{"name":"docker","ecosystem":"Alpine:v3.24","purl":"pkg:apk/alpine/docker?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"20.0.0"},{"fixed":"20.10.3-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-21284.json"}}],"schema_version":"1.9.2","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N"}]}