Bug 1490417 (CVE-2017-12164) - CVE-2017-12164 gdm: lock screen can be circumvented when autologin is set
Summary: CVE-2017-12164 gdm: lock screen can be circumvented when autologin is set
Keywords:
Status: CLOSED NOTABUG
Alias: CVE-2017-12164
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: 1484033
Blocks: 1488875
TreeView+ depends on / blocked
 
Reported: 2017-09-11 13:51 UTC by Cedric Buissart
Modified: 2021-02-17 01:35 UTC (History)
7 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
A flaw was discovered in the gdm where gdm greeter was no longer setting the ran_once boolean during autologin. If autologin was enable for a victim, an attacker could simply select 'login as another user' to unlock their screen.
Clone Of:
Environment:
Last Closed: 2017-09-12 09:29:09 UTC
Embargoed:

Attachments (Terms of Use)

Description Cedric Buissart 2017-09-11 13:51:34 UTC 
The gnome lock screen can be unlocked without needing a password. 

Steps to Reproduce:
1. Enable Automatic Login for your account
2. Reboot
3. Lock screen
4. Click on the log in as another user button below the password prompt.

Actual results:
The screen unlocks without a password being entered.

Expected results:
A selection of other accounts is shown.
Comment 1 Cedric Buissart 2017-09-12 08:53:00 UTC 
This vulnerability is a side effect of upstream https://git.gnome.org/browse/gdm/commit/?id=ff98b28, in gdm-3.24.1.
This patch is not part of gdm as shipped in RHEL 7, 6 or 5. As such, RHEL is not affected by this vulnerability.
Comment 2 Cedric Buissart 2017-09-12 09:13:39 UTC 
Acknowledgments:

Name: Tobias Guggenmos
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