CVE-2011-2012 in Forefront Unified Access Gateway
Summary
by MITRE
Microsoft Forefront Unified Access Gateway (UAG) 2010 Gold, Update 1, Update 2, and SP1 does not properly validate session cookies, which allows remote attackers to cause a denial of service (IIS outage) via unspecified network traffic, aka "Null Session Cookie Crash."
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Analysis
by VulDB Data Team • 11/23/2021
The vulnerability identified as CVE-2011-2012 affects Microsoft Forefront Unified Access Gateway 2010 across multiple update versions and service packs, representing a critical session validation flaw that impacts the gateway's ability to maintain secure and stable operations. This weakness specifically targets the session cookie validation mechanism within the Unified Access Gateway's authentication and access control infrastructure, creating a pathway for malicious actors to exploit the system's session management protocols. The vulnerability manifests when the system fails to properly validate session cookies, leading to a condition where specially crafted network traffic can trigger a cascading failure in the underlying IIS (Internet Information Services) infrastructure. The flaw essentially allows attackers to send malformed or null session cookie data that causes the IIS service to crash or become unresponsive, thereby disrupting access to protected network resources.
The technical exploitation of this vulnerability leverages the absence of proper input validation for session identifiers within the UAG's authentication framework, which operates under the broader context of web application security protocols. This issue directly relates to CWE-20, which categorizes improper input validation as a fundamental weakness in software design and implementation. The vulnerability's impact extends beyond simple service disruption to encompass potential denial of service conditions that can affect enterprise network access and business continuity operations. When an attacker successfully exploits this flaw, the resulting IIS outage can prevent legitimate users from accessing corporate resources, effectively creating a man-in-the-middle scenario where authorized access is blocked by the system's own failure to process session information correctly. The attack vector is particularly concerning as it requires only unspecified network traffic to trigger the vulnerability, making it accessible to remote attackers without requiring special privileges or extensive reconnaissance.
The operational implications of CVE-2011-2012 are significant for organizations relying on Microsoft Forefront UAG for secure remote access and unified access control. This vulnerability can lead to extended periods of service unavailability, particularly in environments where the UAG serves as a critical gateway for remote workers accessing corporate networks. The cascading effect on IIS infrastructure means that the impact extends beyond the immediate access control layer to potentially affect multiple applications and services hosted on the same server infrastructure. Organizations may experience disruptions in productivity, increased incident response overhead, and potential compliance violations if the denial of service conditions affect regulated environments. The vulnerability also creates opportunities for attackers to perform reconnaissance activities or establish persistent access points within the network perimeter, as the system's failure to properly validate session cookies can be exploited to gain insights into the underlying infrastructure configuration and access patterns.
Mitigation strategies for CVE-2011-2012 should prioritize immediate implementation of Microsoft security patches and updates to the Forefront UAG platform, as these address the core session validation flaw in the authentication mechanism. Network administrators should implement additional monitoring and logging controls to detect anomalous session cookie patterns that might indicate exploitation attempts, while also configuring intrusion detection systems to flag unusual traffic patterns targeting the affected gateway components. The vulnerability's classification under the ATT&CK framework for privilege escalation and denial of service operations suggests that defensive measures should include network segmentation to limit the potential impact of successful exploitation attempts. Organizations should also consider implementing additional authentication layers and access control measures to reduce the attack surface, while maintaining comprehensive incident response procedures that account for the specific denial of service conditions that this vulnerability can create. Regular vulnerability assessments and security audits should be conducted to identify similar session validation weaknesses in other components of the unified access infrastructure, as this flaw represents a pattern that may exist in other authentication and access control systems within the enterprise environment.