Bug 1672825 (CVE-2019-3825) - CVE-2019-3825 gdm: lock screen bypass when timed login is enabled
Summary: CVE-2019-3825 gdm: lock screen bypass when timed login is enabled
Status: NEW
Alias: CVE-2019-3825
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard: impact=moderate,public=20190206,repor...
Keywords: Security
Depends On: 1672827 1672829 1672830
Blocks: 1672816
TreeView+ depends on / blocked
 
Reported: 2019-02-06 01:05 UTC by Doran Moppert
Modified: 2019-06-08 23:51 UTC (History)
9 users (show)

(edit)
A vulnerability was discovered in gdm when timed login is enabled in configuration.  An attacker could bypass the lock screen by selecting the timed login user and waiting for the timer to expire at which time they would gain access to the logged-in user's session.
Clone Of:
(edit)
Last Closed:


Attachments (Terms of Use)

Description Doran Moppert 2019-02-06 01:05:08 UTC
Under the right circumstances, after the timed login timeout expires, a running session may get misassociated with the timed login user instead of the user that started the session. Further attempts to log in as the timed login user will instead unlock the misassociated user session.

This only affects X.org since, gdm kills the login screen on wayland after login.

Timed logins must be enabled to expose this vulnerability.

Upstream issue:

https://gitlab.gnome.org/GNOME/gdm/issues/460

Comment 1 Doran Moppert 2019-02-06 01:05:10 UTC
Acknowledgments:

Name: the GNOME Project
Upstream: Burghard Britzke

Comment 2 Doran Moppert 2019-02-06 01:05:12 UTC
Mitigation:

Ensure timed login is not enabled in gdm configuration, by checking the output of:

~~~
grep TimedLogin /etc/gdm/custom.conf
~~~

Comment 4 Doran Moppert 2019-02-06 01:09:02 UTC
Created gdm tracking bugs for this issue:

Affects: fedora-all [bug 1672830]


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