Microsoft Windows contains a vulnerability within the .NET Framework that could allow an unauthenticated, remote attacker to cause a denial of service condition. Updates are available.
Description
Microsoft Windows contains a vulnerability within the .NET Framework that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition.
This vulnerability exists due to errors in managing request scheduling by the ASP.NET component. An unauthenticated, remote attacker could exploit this vulnerability by sending malicious HTTP requests to the vulnerable system. If successful, the attacker could cause the web service to become unresponsive, resulting in a DoS condition.
Microsoft has confirmed this vulnerability in a security bulletin and released software updates that correct it.
Warning Indicators
The following Microsoft systems are vulnerable when running Internet Information Services (IIS) version 7.0 and the .NET Framework versions 2.0 SP2 and prior and 3.5 SP1 and prior in integrated mode:
Windows Vista SP1
Windows Vista x64 Edition SP1
Windows Server 2008 for 32-bit Systems
Windows Server 2008 for x64-based Systems
Windows Server 2008 for Itanium-based Systems
IntelliShield Analysis
Because systems running .NET components as part of IIS are commonly exposed to the Internet or other publicly accessible networks, the source of potential attacks may be very large, increasing the chance of exploitation. However, only systems in certain configurations are affected, possibly making some sites immune to exploits.
If an exploit is successful, the IIS service may become unresponsive to further requests. However, the underlying operating system is unaffected, and still functions normally. Administrator intervention is required to restart the IIS service or application pool in order to restore proper functionality.
The Cisco Applied Intelligence team has created an Applied Mitigation Bulletin to address vulnerabilities that Microsoft disclosed in the August 2009 security bulletin release. This Cisco bulletin, which assists administrators in identifying or mitigating these vulnerabilities using Cisco devices, is available at the following link: Cisco Applied Mitigation Bulletin: Microsoft Security Bulletin Release for August 2009
The update available from Microsoft corrects this vulnerability by modifying ASP.NET request scheduling.
Vendor Announcements
Microsoft has released a security bulletin at the following link: MS09-036
Impact
An unauthenticated, remote attacker could exploit this vulnerability to cause IIS to become unresponsive, resulting in a DoS condition.
Technical Information
This vulnerability exists due to errors in managing request scheduling by the ASP.NET component. Only systems using the .NET Framework running in integrated mode is affected. An unauthenticated, remote attacker could exploit this vulnerability by sending a series of malicious HTTP requests to the vulnerable system. When processed, the requests could cause an error condition that causes the IIS service to become unresponsive, resulting in a DoS condition. However, the underlying operating system is unaffected.
Safeguards
Administrators are advised to apply the applicable software updates.
Administrators may consider configuring the .NET Framework to run in classic mode.
Administrators may consider configuring IIS to use native thread pool process handling.
Administrators are advised to monitor critical systems for service failures.
Administrators may consider using the Microsoft Baseline Security Analyzer (MBSA) scan tool to identify common security misconfigurations and missing security updates on system endpoints.
Patches/Software
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.
Signatures
Cisco Systems Cisco Intrusion Prevention System (IPS) 6.0
The security vulnerability applies to the following combinations of products.
Primary Products:
Microsoft, Inc.
.NET Framework
2.0 SP1, SP2 | 3.5 Base, SP1
Associated Products:
Microsoft, Inc.
Windows Server 2008
Datacenter Edition Base | Datacenter Edition, 64-bit Base | Enterprise Edition Base | Enterprise Edition, 64-bit Base | Essential Business Server Premium Base | Essential Business Server Premium, 64-bit Base | Essential Business Server Standard Base | Itanium-Based Systems Edition Base | Standard Edition Base | Standard Edition, 64-bit Base | Web Server Base | Web Server, 64-bit Base
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