Thursday, November 25, 2010

Two new privilege escalations in Windows

Two new privilege escalations in Windows have appeared this week.

Privilege escalation in the Scheduler
Microsoft has already patched three of the four security holes exploited by Stuxnet, but the fourth hole remains unpatched. Now, an exploit, currently being circulated on the web, exploits the remaining hole in the Windows Task Planner to access protected system directories – even if a user is only logged in with limited access privileges. Experts call this a privilege escalation attack.
According to webDEViL, who developed the exploit, the demo malware works under Windows 7, Vista and Server 2008, both in their 32-bit and in the 64-bit versions.

Privilege escalation in the Registry
Today proof of concept code (source code, with a compiled binary) of a 0-day privilege escalation vulnerability in almost all Windows operating system versions (Windows XP, Vista, 7, Server 2008 ...) has been posted on a popular programming web site.
The vulnerability is a buffer overflow in kernel (win32k.sys) and, due to its nature allows an attacker to bypass User Access Control (UAC) on Windows Vista and 7 operating systems.
What’s interesting is that the vulnerability exist in a function that queries the registry so in order to exploit this the attacker has to be able to create a special (malicious) registry key. Author of the PoC managed to find such a key that can be created by a normal user on Windows Vista and 7 (so, a user that does not even have any administrative privileges).
The PoC code creates such a registry key and calls another library which tries to read the key and during that process it ends up calling the vulnerable code in win32k.sys. Since this is a critical area of the operating system (the kernel allows no mistakes), the published PoC only works on certain kernel versions while on others it can cause a nice BSOD. That being said, the code can be probably relatively easily modified to work on other kernel versions.

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