Microsoft has released a security bulletin and software updates to address the Microsoft Windows Task Scheduler privilege escalation vulnerability.
Microsoft Windows contains a vulnerability that could allow a local attacker to gain elevated privileges.
The vulnerability exists due to insufficient validation performed by the Task Scheduler service on XML schema files. A local attacker could exploit this vulnerability by submitting malicious requests to the system. If successful, the attacker could execute arbitrary code on the system with SYSTEM privileges.
Functional code that exploits this vulnerability is publicly available.
Microsoft confirmed the vulnerability in a security bulletin and released software updates.
The following products are vulnerable:
Windows Vista SP2 and prior
Windows Vista x64 Edition SP2 and prior
Windows Server 2008 for 32-bit Systems SP2 and prior
Windows Server 2008 for x64-based Systems SP2 and prior
Windows Server 2008 Itanium-based Edition SP2 and prior
Windows 7 for 32-bit Systems
Windows 7 for x64-based Systems
Windows Server 2008 R2 for x64-based Systems
Windows Server 2008 R2 for Itanium-based Systems
The attacker must possess credentials sufficient to authenticate to the system prior to exploitation. The access requirement reduces the likelihood of a possible attack.
Reports indicate the vulnerability is being actively exploited in the wild by the W32/Stuxnet-B malicious software documented in IntelliShield Alert 20915. The malicious software exploits a privilege escalation vulnerability that is already present on the system because of another vulnerability or because the attacker has used social engineering techniques to persuade a user to open a malicious executable file.
By exploiting the privilege escalation vulnerability, the malicious software could take complete control over the system. The behavior is most useful on systems such as Windows Vista or Windows 7 where users typically hold only limited privileges, limiting the privileges of any malicious code present on the system.
Microsoft has released a security bulletin at the following link: MS10-092
A local attacker could exploit this vulnerability to execute arbitrary code on the system with SYSTEM privileges, possibly resulting in a complete system compromise.
The vulnerability is due to insufficient validation of XML schema files processed by the Task Scheduler service. The Task Scheduler does not properly check fields in unspecified XML schema files that could be accessed and manipulated via the Component Object Model (COM) interface.
A local attacker could exploit this vulnerability by submitting malicious requests to the COM interface, allowing the attacker to manipulate a valid XML schema file. The processing of the modified XML schema files by the Task Scheduler could allow the attacker to load tasks in the Task Scheduler that would run with SYSTEM privileges.
Administrators are advised to apply the available software updates.
Administrators are advised to allow only trusted users to access local systems.
Administrators are advised to implement physical security for production servers.
Administrators are advised to monitor affected systems.
Microsoft customers can obtain updates directly by using the links in the security bulletin. These updates are also distributed by Windows automatic update features and available on the Windows Update website. Microsoft Windows Server Update Services (WSUS), Systems Management Server, and System Center Configuration Manager can assist administrators in deploying software updates.
Version 2, November 22, 2010, 3:22 PM: Functional code that exploits the Microsoft Windows Task Scheduler privilege escalation vulnerability is publicly available.
Version 1, October 25, 2010, 9:13 AM: Multiple Microsoft Windows operating systems contain a vulnerability that could allow an unprivileged, local attacker to gain elevated privileges. Updates are not available.
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