CVE-2011-1896 in Forefront Unified Access Gateway
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Microsoft Forefront Unified Access Gateway (UAG) 2010 Gold, Update 1, Update 2, and SP1 allows remote attackers to inject arbitrary web script or HTML via unspecified vectors, aka "ExcelTable Reflected XSS Vulnerability."
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Analysis
by VulDB Data Team • 11/23/2021
The CVE-2011-1896 vulnerability represents a critical cross-site scripting flaw discovered in Microsoft Forefront Unified Access Gateway 2010 versions including Gold, Update 1, Update 2, and Service Pack 1. This vulnerability specifically affects the ExcelTable component within the UAG platform, creating a reflected XSS attack vector that enables remote threat actors to execute malicious web scripts or HTML code within the context of user sessions. The vulnerability stems from inadequate input validation and output encoding mechanisms within the unified access gateway's web interface, particularly when handling ExcelTable-related requests. The flaw manifests when user-supplied input containing malicious scripts is reflected back to the victim's browser without proper sanitization or encoding, creating an exploitable condition that can persist across multiple user interactions.
This vulnerability operates through reflected XSS mechanisms where malicious input is immediately reflected back to the user's browser without sufficient security controls to prevent script execution. The attack typically involves crafting malicious URLs or form submissions containing script payloads that are then processed by the UAG server and returned to the victim's browser in the response. The ExcelTable component specifically handles spreadsheet data processing and rendering, making it a prime target for attackers seeking to inject malicious code that could execute within the context of authenticated users. The vulnerability's impact is amplified by the fact that UAG serves as a unified access gateway, often providing access to enterprise resources and sensitive data, making successful exploitation potentially devastating for organizational security.
The operational impact of CVE-2011-1896 extends beyond simple script injection, as attackers can leverage this vulnerability to perform session hijacking, steal authentication tokens, redirect users to malicious sites, or execute arbitrary commands within the victim's browser context. The reflected nature of the vulnerability means that attacks can be delivered through phishing emails, malicious links, or compromised web pages that direct users to the vulnerable UAG interface. This creates a significant risk for enterprise environments where UAG serves as a critical access control point, potentially allowing attackers to bypass traditional security controls and gain unauthorized access to internal resources. The vulnerability affects the broader Microsoft ecosystem and aligns with CWE-79, which specifically addresses cross-site scripting flaws in web applications, and can be mapped to ATT&CK technique T1566.001 for initial access through spearphishing attachments or links.
Organizations affected by this vulnerability should immediately implement mitigations including deploying web application firewalls, implementing proper input validation and output encoding controls, and applying Microsoft security updates as soon as they become available. The recommended approach involves configuring the UAG to properly sanitize all user inputs, particularly those related to ExcelTable processing, and implementing Content Security Policy headers to prevent script execution. Additionally, network segmentation and monitoring solutions should be deployed to detect and prevent exploitation attempts. Security teams should conduct comprehensive vulnerability assessments to identify all instances of the affected UAG versions and ensure proper patch management procedures are in place to prevent similar vulnerabilities in the future. The remediation process should include thorough testing of security controls to ensure that the XSS vulnerability is completely eliminated without introducing new functional issues in the unified access gateway environment.