Microsoft has released a security bulletin and software updates to address the Microsoft Internet Information Services authentication bypass vulnerability.
Microsoft Internet Information Services version 5.1 when running on Windows XP platforms contains a vulnerability that could allow an unauthenticated, remote attacker to bypass authentication and gain unauthorized access.
The vulnerability is due to improper processing of malformed values with URLs. An unauthenticated, remote attacker could exploit the vulnerability by sending a malicious URL to a targeted system. If successful, the attacker could gain unauthorized access to a protected directory.
Proof-of-concept code that exploits this vulnerability is publicly available.
Microsoft has confirmed this vulnerability in a security bulletin and released software updates.
Microsoft IIS 5.1 running on Windows XP SP3 and prior is vulnerable.
Reports indicate that only IIS 5.1 is vulnerable. This software is included only with Windows XP systems and is not installed by default. Additionally, systems are only affected when basic authentication is configured, which is considered generally unsafe because passwords are sent in plain text to the targeted system. Windows XP systems are also unlikely to host critical sites or applications, greatly reducing the potential for affected systems.
Microsoft has released a security bulletin at the following link: MS10-065
An unauthenticated, remote attacker could exploit this vulnerability to bypass authentication protections on the web server, allowing the attacker to gain unauthorized access to protected pages.
The vulnerability is due to improper processing of values sent by URL. An unauthenticated, remote attacker could exploit the vulnerability by sending a URL containing malicious values to a web server. The processing of the request could cause the application to return the contents of a password-protected web directory, allowing the attacker to access protected content.
Administrators are advised to apply the available software updates.
Administrators may consider employing authentication methods other than basic authentication.
Administrators are advised to monitor critical 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, July 6, 2010, 8:24 AM: Proof-of-concept code that exploits the Microsoft Internet Information Services authentication bypass vulnerability is publicly available.
Version 1, July 2, 2010, 3:20 PM: Microsoft Internet Information Services when running on Windows XP contains a vulnerability that could allow an unauthenticated, remote attacker to bypass authentication and gain unauthorized access. Updates are not available.
The security vulnerability applies to the following combinations of products.
Internet Information Services (IIS)
Home Edition Base, SP1, SP2, SP3 | Professional Edition Base, SP1, SP2, SP3 | Professional x64 (AMD/EM64T) Base, SP2
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