Microsoft Internet Security and Acceleration Server contains a vulnerability that could allow an unauthenticated, remote attacker to bypass security restrictions and gain unauthorized access to a vulnerable system. Updates are available.
Microsoft Internet Security and Acceleration (ISA) Server 2006 SP1 and prior contain a vulnerability that could allow an unauthenticated, remote attacker to bypass security restrictions and gain unauthorized access to a vulnerable system.
This vulnerability is due to errors when the vulnerable server handles Radius One-Time Password (OTP) authentication requests. An unauthenticated, remote attacker could exploit this vulnerability by sending a malicious request to the system. If an exploit is successful, the attacker could gain unauthorized access to restricted resources.
Microsoft has confirmed this vulnerability in a security bulletin and released updated software.
Microsoft Internet Security and Acceleration Server 2006 SP1 and prior are vulnerable.
To exploit this vulnerability, an attacker must be able to make authentication attempts to the vulnerable system using the name of an existing administrative account. The attacker must know the account name before the attack. The attacker may also require access to internal networks to send the authentication request, which could reduce the potential for exploitation.
If an exploit is successful, the attacker could bypass authentication and access restricted resources. The attacker could completely compromise systems protected by the ISA Server.
The Cisco Applied Intelligence team has created an Applied Mitigation Bulletin to address vulnerabilities that Microsoft disclosed in the July 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 for July 2009
The update available from Microsoft corrects this vulnerability by rejecting authentication requests that cannot be processed by Radius OTP.
Microsoft has released a security bulletin at the following link: MS09-031
An unauthenticated, remote attacker could exploit this vulnerability to bypass security restrictions and gain unauthorized access to resources on a vulnerable system.
This vulnerability is due to errors when the vulnerable server handles Radius OTP authentication requests. ISA Server may attempt to authenticate requests using the HTTP Basic authentication method. The processing of a specifically formed authentication request could be misinterpreted as valid by the application, allowing unauthorized access. Only systems that use Radius OTP configured to use HTTP Basic authentication as a fallback method are vulnerable to exploitation.
An unauthenticated, remote attacker who knows the account name of an administrative account could exploit this vulnerability by sending a malicious authentication request to the affected system. The processing of the malicious request could grant the attacker approved access to the application or systems that are protected by the application. This behavior could give the attacker unauthorized access to protected resources.
Administrators are advised to apply the appropriate update.
Administrators are advised to restrict network access to affected systems.
Administrators may consider disabling Basic authentication fallback.
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.
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