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
Keywords:
Status: CLOSED ERRATA
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:
Depends On: 1672827 1672829 1672830
Blocks: 1672816
TreeView+ depends on / blocked
 
Reported: 2019-02-06 01:05 UTC by Doran Moppert
Modified: 2021-02-16 22:24 UTC (History)
9 users (show)

Fixed In Version: gdm 3.31.4
Doc Type: If docs needed, set a value
Doc Text:
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:
Environment:
Last Closed: 2020-04-28 16:32:26 UTC
Embargoed:

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System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2020:1766 0 None None None 2020-04-28 15:50:51 UTC

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]
Comment 7 Doran Moppert 2019-02-07 23:44:29 UTC 
External References:

https://gitlab.gnome.org/GNOME/gdm/issues/460
https://gitlab.gnome.org/GNOME/gdm/merge_requests/58
Comment 8 errata-xmlrpc 2020-04-28 15:50:50 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2020:1766 https://access.redhat.com/errata/RHSA-2020:1766
Comment 9 Product Security DevOps Team 2020-04-28 16:32:26 UTC 
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):

https://access.redhat.com/security/cve/cve-2019-3825
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