Effects 

MS09-026 is not categorized as virus, worm, Trojan or backdoor. It is an important vulnerability in the Windows remote procedure call (RPC) on Windows Server 2008/Vista/2003/XP/2000 computers, which allows to gain local privilege escalation.

There is a vulnerability when the RPC Marshalling Engine does not update its internal state in an appropriate way.

The RPC Marshalling Engine, also known as NDR, provides a common RPC interface between RPC clients and servers.

If exploited successfully, MS09-026 allows to gain unauthorized privileges on a computer or network. An example of privilege elevation would be an unprivileged user who could manage to be added to the Administrator's group. In such case, the hacker could take complete control of the system: create, modify or delete files, install programs, create new user accounts, etc.

MS09-026 is usually exploited by creating a specially crafted RPC message and seding it to an affected system over an affected TCP or UDP port.

If you have a Windows Server 2008/Vista/2003/XP/2000 computer, it is recommended to download and apply the security patch for this vulnerability. Click here to access the web page for downloading the patch.

Bear in mind that this security patch replaces a previous one, called MS07-058.