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Credit:
The information has been provided by iDEFENSE.
The original article can be found at: http://www.idefense.com/intelligence/vulnerabilities/display.php?id=411
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Vulnerable Systems:
* X.org server version 6.8.2
The vulnerability specifically exists in the handling of 'CMap' and 'CIDFont' font data. When parsing this information no checks are made that the count of items for the 'begincodespacerange', 'cidrange' and 'notdefrange' sections.
In addition to a 'standard' integer overflow, the implementation of 'vm_alloc()' makes it possible to overwrite memory before the allocated region.
Analysis:
Successful local exploitation allows an attacker to execute arbitrary as the root user. In order to exploit this vulnerability an attacker would require the ability to send commands to an affected X server. This typically requires access to the console, or access to the same account as a user who is on the console. One method of gaining the required access would be to remotely exploit a vulnerability in, for example, a graphical web browser. This would then allow an attacker to exploit this vulnerability and elevate their privileges to root.
Workaround:
Access to the vulnerable code can be prevented by removing the entry for the Type1 font module from your Xservers configuration file, often stored in /etc/X11 and named xorg.conf or XF86Config-4. To do this, remove the following line from the 'Module' section:
Load "type1"
This will prevent Type 1 fonts from loading, which may affect the appearance or operation of some applications.
Vendor response:
The X.Org foundation has addressed this vulnerability with libXfont version 1.2.1. Additionally, patches have been made available for older releases.
"The XFree86 Project Inc. is making available a source patch available at ftp://xfree86.org/pub/XFree86/4.6.0/fixes/fix-01 that, in part, addresses this vulnerability."
CVE Information:
CVE-2006-3740
Disclosure Timeline:
08/25/2006 Initial vendor notification
08/25/2005 Initial vendor response (X.Org)
09/10/2006 Initial vendor response (XFree86)
09/12/2006 Coordinated public disclosure
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