CVE-2006-4909 in Guard
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Cisco Guard DDoS Mitigation Appliance before 5.1(6), when anti-spoofing is enabled, allows remote attackers to inject arbitrary web script or HTML via certain character sequences in a URL that are not properly handled when the appliance sends a meta-refresh.
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Analysis
by VulDB Data Team • 07/08/2019
The vulnerability identified as CVE-2006-4909 represents a critical cross-site scripting flaw in Cisco Guard DDoS Mitigation Appliances running firmware versions prior to 5.1(6). This security weakness specifically manifests when the appliance operates with anti-spoofing enabled, creating a dangerous condition where malicious actors can exploit improperly handled character sequences within URLs to inject arbitrary web scripts or HTML content. The vulnerability stems from the appliance's failure to adequately sanitize input during the meta-refresh header generation process, which occurs when the device redirects users to a specific URL.
The technical implementation of this flaw involves the appliance's handling of URL parameters and character sequences that are processed during network traffic management operations. When anti-spoofing features are active, the system generates meta-refresh headers to redirect users, but these headers do not properly escape or validate special characters that could be interpreted as executable script code. This creates an injection point where an attacker can craft malicious URLs containing script tags or other HTML elements that get embedded into the meta-refresh header and subsequently executed in the victim's browser. The vulnerability falls under CWE-79, which specifically addresses Cross-Site Scripting flaws, and demonstrates a classic case of improper input validation and output encoding.
The operational impact of this vulnerability extends beyond simple script injection, as it provides attackers with the capability to perform session hijacking, redirect users to malicious sites, or execute arbitrary commands within the context of the victim's browser session. The affected appliance's role in DDoS mitigation makes this particularly dangerous, as attackers could potentially exploit this weakness to disrupt legitimate network traffic or gain unauthorized access to the appliance's administrative interface. The meta-refresh mechanism serves as a critical attack vector since it is commonly used in legitimate web applications for automatic redirection, making the vulnerability more likely to be exploited in real-world scenarios.
Organizations utilizing Cisco Guard DDoS Mitigation Appliances must implement immediate mitigation strategies including firmware updates to version 5.1(6) or later, which contain the necessary patches to address the input sanitization issues. Network administrators should also consider implementing additional monitoring and filtering mechanisms to detect suspicious URL patterns that might indicate attempted exploitation. The vulnerability aligns with ATT&CK technique T1059.007, which covers scripting through web shell execution, and demonstrates how network infrastructure devices can serve as attack vectors for broader web-based exploitation campaigns. Regular security assessments and input validation reviews should be conducted to ensure similar vulnerabilities are not present in other network management systems.