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CVE-2020-27837

Published: 28 December 2020

A flaw was found in GDM in versions prior to 3.38.2.1. A race condition in the handling of session shutdown makes it possible to bypass the lock screen for a user that has autologin enabled, accessing their session without authentication. This is similar to CVE-2017-12164, but requires more difficult conditions to exploit.

Priority

Low

CVSS 3 base score: 6.4

Status

Package Release Status
gdm3
Launchpad, Ubuntu, Debian
Upstream
Released (3.38.2.1-1)
Ubuntu 21.10 (Impish Indri) Needed

Ubuntu 21.04 (Hirsute Hippo) Needed

Ubuntu 20.04 LTS (Focal Fossa) Needed

Ubuntu 18.04 LTS (Bionic Beaver) Not vulnerable

Ubuntu 16.04 ESM (Xenial Xerus) Not vulnerable

Ubuntu 14.04 ESM (Trusty Tahr) Does not exist

Patches:
Upstream: https://gitlab.gnome.org/GNOME/gdm/-/commit/dcdbaaa04012541ad2813cf83559d91d52f208b9 (master)
Upstream: https://gitlab.gnome.org/GNOME/gdm/-/commit/9b6d9b24a5f69674447c7bc9aacfab0988b914bd (3.38.2.1)

Notes

AuthorNote
mdeslaur
unlikely scenario, requires autologin to be enabled and for a
session to crash but then still work. Setting priority to "low"

References

Bugs