Original URL: http://www.theregister.co.uk/2013/11/28/winxp_0day/

Think unpatched Win XP hole's not a big deal? Hope you trust your local users

Vulnerability used to breathe life into Adobe Reader exploit, Microsoft warns

By John Leyden

Posted in Security, 28th November 2013 12:59 GMT

An unpatched vulnerability in Windows XP and Windows Server 2003 creates a means for hackers to gain admin rights on vulnerable Windows XP machines, Microsoft warned on Wednesday.

The zero-day local privilege escalation vulnerability is not suitable for remote code execution but might allow a standard user account to execute code in the kernel. As such, the bug is not that much use on its own, but potentially troublesome when mixed in a cocktail with other software vulnerabilities in order to formulate workable attacks.

Unfortunately this has already happened and the vulnerability has already been used in anger in conjunction with an Adobe Reader exploit to target a recently patched vulnerability in the widely used PDF reader software, anti-malware firm FireEye warns. Simply put, the Windows bug allows hackers to bypass Adobe's sandbox defences but only on older versions of Reader.

The combined exploit targets Adobe Reader 9.5.4, 10.1.6, 11.0.02 and prior on Windows XP SP3. XP users who are running the latest versions of Adobe Reader are immune from the attack, so upgrading to the latest version of Abode Reader is probably the best way of blocking potential attacks. Windows Server 2003 is also vulnerable to same privilege escalation vulnerability but are not anywhere near as at risk of attack (unless a BOFH opens a email containing rigged PDFs from a vulnerable server, or other unlikely scenarios), hence the focus on the millions upon millions of vulnerable Win XP systems.

Microsoft plays down the seriousness of the vulnerability while admitting it has been abused in "limited, targeted attacks".

The Adobe flaw was patched in August, according to cloud security firm Qualys.

"Users that have the latest version of Adobe Reader are immune to the attack, as well as users that are running on Windows Vista or later," Wolfgang Kandek, CTO a Qualys, explains in a blog post. ®