CVE-2021-21284

NameCVE-2021-21284
DescriptionIn 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.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, bugtraq, EDB, Metasploit, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, Mageia, GitHub code/issues, web search, more)
ReferencesDSA-4865-1
NVD severitylow

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
docker.io (PTS)buster18.09.1+dfsg1-7.1+deb10u2vulnerable
buster (security)18.09.1+dfsg1-7.1+deb10u3fixed
bullseye20.10.3+dfsg1-2fixed
sid20.10.4+dfsg1-1fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
docker.iosourcebuster18.09.1+dfsg1-7.1+deb10u3DSA-4865-1
docker.iosource(unstable)20.10.3+dfsg1-1

Notes

https://github.com/moby/moby/security/advisories/GHSA-7452-xqpj-6rpc
https://github.com/moby/moby/commit/1342c51d5e809d2994e6f7e490c8d2b3b12c28ae (v19.03)
https://github.com/moby/moby/commit/5eff67a2c294b7e72607e0949ebc0de21710e4d3 (v19.03)
https://github.com/moby/moby/commit/67de83e70bca92ae6a08e28a03b3fc8fcca9f3f1 (v19.03)

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