CVE-2009-1202 in ASA
Summary
by MITRE
WebVPN on the Cisco Adaptive Security Appliances (ASA) device with software 8.0(4), 8.1.2, and 8.2.1 allows remote attackers to bypass certain protection mechanisms involving URL rewriting and HTML rewriting, and conduct cross-site scripting (XSS) attacks, by modifying the first hex-encoded character in a /+CSCO+ URI, aka Bug ID CSCsy80705.
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Analysis
by VulDB Data Team • 02/11/2017
The vulnerability described in CVE-2009-1202 represents a critical security flaw in Cisco Adaptive Security Appliances (ASA) devices that affects specific software versions including 8.0(4), 8.1.2, and 8.2.1. This issue resides within the WebVPN functionality of the ASA platform, which serves as a crucial component for remote access and secure network connectivity. The vulnerability specifically targets the URL rewriting and HTML rewriting mechanisms that are essential for maintaining security boundaries between internal networks and external users accessing services through the ASA device. The flaw allows malicious actors to manipulate the initial hex-encoded character within the /+CSCO+ URI structure, effectively circumventing the intended security controls that should prevent unauthorized access and malicious content injection.
The technical implementation of this vulnerability stems from insufficient input validation and sanitization within the ASA's WebVPN processing logic. When the ASA processes requests containing the /+CSCO+ URI pattern, it fails to properly validate the hex-encoded character sequence that precedes the standard URI components. This oversight creates a pathway for attackers to modify the initial character of the encoded URI, which subsequently alters how the device processes and rewrites URLs and HTML content. The vulnerability operates at the application layer of the network stack and leverages the inherent trust placed in the ASA's security mechanisms to process and filter web content. This flaw directly relates to CWE-79 Cross-site Scripting and CWE-20 Improper Input Validation, as it allows attackers to inject malicious code through manipulated URI sequences that bypass the device's security filters.
The operational impact of this vulnerability is severe and multifaceted, as it enables remote attackers to execute cross-site scripting attacks against users accessing the network through the compromised ASA device. Attackers can craft malicious URIs that, when processed by the vulnerable ASA, result in the injection of malicious JavaScript code into web pages served to authenticated users. This capability allows for session hijacking, data theft, and further exploitation of the compromised network environment. The vulnerability affects the fundamental security posture of the ASA device, as it undermines the device's ability to properly filter and sanitize content passing through its WebVPN functionality. The implications extend beyond simple XSS attacks, as successful exploitation could provide attackers with access to internal network resources, potentially leading to complete network compromise and data breaches.
Organizations affected by this vulnerability should implement immediate mitigation strategies to protect their network infrastructure. The primary recommendation involves upgrading to Cisco ASA software versions that contain patches addressing this specific vulnerability, typically versions released after the initial disclosure. Network administrators should also consider implementing additional monitoring and logging mechanisms to detect anomalous URI patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper input validation and the potential consequences of insufficient sanitization in security-critical components. Organizations should conduct thorough security assessments of their ASA configurations and review existing access controls to ensure that the exploitation of such vulnerabilities does not lead to further compromise of their network infrastructure. This vulnerability also highlights the necessity of maintaining current security patches and following industry best practices such as those outlined in the NIST Cybersecurity Framework and MITRE ATT&CK framework for preventing and detecting such exploitation techniques.