UBUNTU-CVE-2021-21284

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UBUNTU-CVE-2021-21284

Summary:

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/<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.

References: https://ubuntu.com/security/CVE-2021-21284, https://github.com/moby/moby/security/advisories/GHSA-7452-xqpj-6rpc, https://docs.docker.com/engine/release-notes/#20103, https://github.com/moby/moby/commit/64bd4485b3a66a597c02c95f5776395e540b2c7c, https://github.com/moby/moby/releases/tag/v19.03.15, https://github.com/moby/moby/releases/tag/v20.10.3, https://ubuntu.com/security/notices/USN-5032-1, https://ubuntu.com/security/notices/USN-5032-2, https://www.cve.org/CVERecord?id=CVE-2021-21284