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Security Best Practice: Protect Yourself from Invalid IIS ASP.Net URI Character Requests

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Check Point Reference: SBP-2009-15
Date Published:
Severity:
Last Updated:
Source: Microsoft Security Bulletin MS09-036
Industry Reference(s): CVE-2009-1536
Protection Provided by: Security Gateway
  • R70
VPN-1
  • NGX R65
VSX
  • NGX R65
IPS-1
  • IPS-1
  • IPS-1 NGX R65
Who is Vulnerable?
Microsoft .NET Framework 2.0 on:
Windows Vista
Windows Vista x64 Edition
Windows Server 2008

Microsoft .NET Framework 2.0 SP1 on:
Windows Vista
Windows Vista SP1
Windows Vista x64 Edition
Microsoft .NET Framework 2.0 SP1 onWindows Vista x64 Edition SP1
Windows Server 2008
Windows Server 2008 x64 Edition
Windows Server 2008 (Itanium)

Microsoft .NET Framework 2.0 SP2 on:
Windows Vista
Windows Vista SP1
Windows Vista x64 Edition
Windows Vista x64 Edition SP1
Windows Server 2008
Windows Server 2008 x64 Edition
Windows Server 2008 (Itanium)

Vulnerability Description
A denial of service vulnerability has been reported in ASP.NET. ASP.NET is a collection of technologies within the.NET Framework that enable developers to build Web applications and XML Web Services. A remote attacker may exploit this issue to cause a vulnerable server to become non-responsive.
Vulnerability Details
This vulnerability is due to an error in ASP.NET that fails to correctly manage request scheduling. An attacker could exploit this vulnerability by creating a specially crafted series of anonymous HTTP requests to an affected system. Successful exploitation of this vulnerability could cause the application pool on the affected Web server to become non-responsive. As a result, Web pages that use ASP.NET in the same application pool would no longer be reachable and would return an HTTP error.

Protection Overview
This protection will detect and block IIS ASP.Net requests with invalid characters in the URI.

In order for the protection to be activated, update your Security Gateway/VPN-1 product to the latest IPS/SmartDefense update. For information on how to update IPS/SmartDefense, go to SBP-2006-05, Protection tab and select the version of your choice.

To configure the defense, select your product from the list below and follow the related protection steps.

Security Gateway R70

How Can I Protect My Network?
1. In the IPS tab, click Protections > By Protocol > Application Intelligence > Web Servers > IIS.
2. In the right pane, double-click the Invalid IIS ASP.Net URI Character Request protection.
3. In the Protection Details window, click on Edit. Choose the protection's Action (Override IPS Policy with: Prevent/Detect), and apply Additional Settings.
4. Install policy on all modules.

How Do I Know if My Network is Under Attack?
SmartView Tracker will log the following entries:

Attack Name: Web Server Enforcement Violation
Attack Information: Invalid IIS ASP.Net URI character request

VPN-1 NGX R65

How Can I Protect My Network?
1. In the SmartDefense tab, click Application Intelligence > Web Servers > IIS > Invalid IIS ASP.Net URI Character Request.
2. In the configuration pane, under Settings > Mode, check Active.
3. Install policy on all modules.

How Do I Know if My Network is Under Attack?
SmartView Tracker will log the following entries:

Attack Name: Web Server Enforcement Violation
Attack Information: Invalid IIS ASP.Net URI character request

VPN-1 VSX NGX R65

How Can I Protect My Network?
1. In the SmartDefense tab, click Application Intelligence > Web Servers > IIS > Invalid IIS ASP.Net URI Character Request.
2. In the configuration pane, under Settings > Mode, check Active.
3. Install policy on all modules.

How Do I Know if My Network is Under Attack?
SmartView Tracker will log the following entries:

Attack Name: Web Server Enforcement Violation
Attack Information: Invalid IIS ASP.Net URI character request

IPS-1 & IPS-1 NGX R65

How Can I Protect My Network?
1. In the IPS-1 Policy Manager, click on the Protection tab.
2. In the Protection tree, click Web Intelligence > WWW 2, and select the IIS Attacks protection group.
3. Click ASP.NET Denial of Service (CVE-2009-1536) (IPS-1 NGX R65 only).
4. In the configuration pane, under Settings, check Active.
5. Click on Install Policy.

How Do I Know if My Network is Under Attack?
Upon attack, the following entries will be logged:

Alert Name: Attacks against IIS web servers
Description: ASP.NET Denial of Service (CVE-2009-1536)