CVE-2006-3101 in Secure Access Control Server
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in LogonProxy.cgi in Cisco Secure ACS for UNIX 2.3 allows remote attackers to inject arbitrary web script or HTML via the (1) error, (2) SSL, and (3) Ok parameters.
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Analysis
by VulDB Data Team • 06/21/2025
The vulnerability described in CVE-2006-3101 represents a critical cross-site scripting flaw in Cisco Secure Access Control Server version 2.3 for UNIX systems. This vulnerability specifically affects the LogonProxy.cgi component which serves as a web interface for authentication and access control functions. The flaw exists in how the application processes user input parameters, creating an avenue for malicious actors to inject arbitrary web scripts or HTML code into the application's response. The vulnerability impacts three specific parameters: error, SSL, and Ok, which are commonly used in authentication workflows and error handling mechanisms. This type of vulnerability falls under the CWE-79 category of Cross-Site Scripting, which is classified as a fundamental web application security weakness that has been consistently identified as one of the most prevalent security flaws in web applications.
The technical exploitation of this vulnerability occurs when an attacker crafts malicious input containing script code and submits it through any of the three vulnerable parameters. When the LogonProxy.cgi script processes these parameters without proper sanitization or output encoding, the injected scripts become part of the web page response and are executed in the context of other users' browsers. This creates a persistent threat where authenticated users who view the affected page could have their sessions hijacked, their data compromised, or they could be redirected to malicious websites. The attack vector is particularly dangerous because it operates entirely within the web application layer, requiring no special privileges or system access beyond normal web browsing capabilities. The vulnerability demonstrates a classic lack of input validation and output encoding practices that are fundamental to secure web development, aligning with ATT&CK technique T1203 which involves the use of web shells and client-side attacks.
The operational impact of this vulnerability extends beyond simple script injection, as it can enable more sophisticated attacks such as session hijacking, credential theft, and data exfiltration from authenticated users. In a corporate environment using Cisco Secure ACS, this vulnerability could allow attackers to gain unauthorized access to network resources, potentially compromising the entire access control infrastructure. The affected parameters are commonly used during authentication flows, meaning that any user attempting to log in or encountering authentication errors could be exposed to the malicious scripts. The vulnerability affects the core functionality of the access control system, undermining the trust model that organizations rely upon for network security. Organizations using this version of Cisco Secure ACS would face significant risk to their network perimeter security, as successful exploitation could provide attackers with a foothold to escalate privileges and access sensitive network resources. This vulnerability also impacts the integrity of the authentication process, potentially allowing attackers to bypass security controls or manipulate access decisions.
Mitigation strategies for this vulnerability should include immediate patching of the Cisco Secure ACS software to the latest available version that addresses the XSS flaw. Organizations should also implement proper input validation and output encoding mechanisms to prevent script injection attacks, ensuring that all user-supplied data is properly sanitized before being processed or displayed. Network segmentation and monitoring should be enhanced to detect unusual authentication patterns or script injection attempts. The implementation of Content Security Policy headers can provide additional protection against XSS attacks by restricting the sources from which scripts can be loaded. Security teams should also conduct thorough vulnerability assessments of their access control systems and implement web application firewalls to monitor and filter malicious traffic. Regular security updates and patch management processes should be established to prevent similar vulnerabilities from occurring in other components of the access control infrastructure. This vulnerability highlights the importance of maintaining up-to-date security measures and demonstrates how even critical infrastructure components can contain exploitable flaws that require immediate attention.