Vulnerability in Linux pam_console module

vendor:

pam_console module

by:

bkw1a@virginia.edu and Andreas Hasenack

7.2

CVSS

HIGH

Privilege Escalation

264

CWE

Product Name: pam_console module

Affected Version From: N/A

Affected Version To: N/A

Patch Exists: NO

Related CWE: N/A

CPE: N/A

Metasploit: N/A

Other Scripts: N/A

Tags: N/A

CVSS Metrics: N/A

Nuclei References: N/A

Nuclei Metadata: N/A

Platforms Tested: Linux

2002

Vulnerability in Linux pam_console module

There is a vulnerability in the Linux pam_console module that could allow an attacker to remotely reboot the workstation or perform other actions limited to local users. If a workstation is configured to use a display manager (xdm, gdm, kdm, etc.) AND has XDMCP enabled, it is possible for a user who logs in remotely to use Xnest -query to log in on display :1, which is recognized as the system console. This vulnerability is only present if the workstation is running a graphical login manager such as gdm or kdm.

Mitigation:

Disable XDMCP on the workstation and ensure that the graphical login manager is not running.

Source

Exploit-DB raw data:

source: https://www.securityfocus.com/bid/1513/info

There is a vulnerability in the Linux pam_console module that could allow an attacker to remotely reboot the workstation or perform other actions limited to local users.
If a workstation is configured to use a display manager (xdm, gdm, kdm, etc.) AND has XDMCP enabled, it is possible for a user who logs in remotely to use Xnest -query to log in on display :1, which is recognized as the system console. This vulnerability is only present if the workstation is running a graphical login manager such as gdm or kdm. 


This description of how to replicate the problem was posted to RedHat's Bugzilla bug-tracking system by bkw1a@virginia.edu:
1. ssh into the server, allowing ssh to establish a secure forwarded X connection. If no one else is using display number 0, you'll end up with a DISPLAY value of "host:0.0".
2. Invoke "Xnest -query localhost" on the remote machine.
3. Log in, starting a Gnome session.
4. From the Gnome panel, select "logout". You'll be presented with the option of shutting down or rebooting the server.

Another description, this one from Andreas Hasenack <andreas@conectiva.com.br>:
1. login remotely (X -broadcast) (have gdm, kdm, whatever running with XDMCP enabled somewhere)
2. after login, start Xnest with -broadcast again, for example
3. login again, now you will be using display :1
4. this is treated as a console user, and commands only available to console users can be run, such as reboot.