CVE-2021-3493

NameCVE-2021-3493
DescriptionThe overlayfs implementation in the linux kernel did not properly validate with respect to user namespaces the setting of file capabilities on files in an underlying file system. Due to the combination of unprivileged user namespaces along with a patch carried in the Ubuntu kernel to allow unprivileged overlay mounts, an attacker could use this to gain elevated privileges.
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)
NVD severityhigh

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
linux (PTS)stretch4.9.228-1fixed
stretch (security)4.9.272-2fixed
buster4.19.208-1vulnerable
buster (security)4.19.194-3vulnerable
bullseye5.10.70-1fixed
bullseye (security)5.10.46-5fixed
bookworm5.14.9-2fixed
sid5.14.12-1fixed

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

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
linuxsourcestretch(not affected)
linuxsource(unstable)5.10.38-1

Notes

[stretch] - linux <not-affected> (Unprivileged users cannot mount overlayfs)
https://www.openwall.com/lists/oss-security/2021/04/16/1

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