CVE-2005-1155 in Firefox
Summary
by MITRE
The favicon functionality in Firefox before 1.0.3 and Mozilla Suite before 1.7.7 allows remote attackers to execute arbitrary code via a <LINK rel="icon"> tag with a javascript: URL in the href attribute, aka "Firelinking."
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Analysis
by VulDB Data Team • 12/17/2024
The vulnerability identified as CVE-2005-1155 represents a critical cross-site scripting flaw in the favicon handling mechanism of Mozilla Firefox versions prior to 1.0.3 and the Mozilla Suite versions before 1.7.7. This security weakness stems from the browser's improper validation of favicon URLs, specifically when processing the rel="icon" attribute within HTML link tags. The vulnerability is categorized under CWE-79 as a cross-site scripting attack, where malicious code can be injected through improperly sanitized user input. The attack vector exploits the browser's automatic favicon retrieval process, which occurs when users visit web pages containing malicious favicon references.
The technical flaw manifests when a web page includes a link tag with the rel="icon" attribute pointing to a javascript: URL in the href attribute. When Firefox encounters such a tag, it attempts to retrieve the favicon resource automatically, executing the embedded javascript code in the process. This behavior bypasses normal security restrictions that would typically prevent execution of javascript code from external sources. The vulnerability is particularly dangerous because it leverages the browser's legitimate favicon functionality to deliver malicious payloads, making it difficult for users to distinguish between benign and malicious content. The attack operates at the application layer and can be classified under ATT&CK technique T1203 as "Exploitation for Client Execution" where adversaries use web-based attacks to execute code on target systems.
The operational impact of this vulnerability is severe as it allows remote attackers to execute arbitrary code on affected systems with the privileges of the browser user. Successful exploitation could lead to complete system compromise, data theft, or further lateral movement within a network. The vulnerability affects a wide range of users since favicon functionality is commonly used across the web, and the attack requires no user interaction beyond visiting a malicious webpage. The risk is amplified because the attack occurs automatically during page loading, making it nearly impossible for users to defend against without proper browser updates. Security researchers noted that the vulnerability was particularly concerning due to its ability to bypass standard security mechanisms and execute code through seemingly innocuous HTML elements.
Mitigation strategies for CVE-2005-1155 primarily involve immediate patching of affected browser versions to the latest secure releases. Users should ensure their browsers are updated to Firefox 1.0.3 or later and Mozilla Suite 1.7.7 or later, which contain fixes for the favicon processing logic. Additionally, administrators can implement web application firewalls that filter out javascript: URLs in favicon references or configure browser security policies to disable automatic favicon retrieval. Network-level protections can include filtering of favicon-related requests or implementing content security policies that restrict execution of javascript code from external sources. The vulnerability highlights the importance of input validation and the principle of least privilege in web application security, emphasizing that even seemingly benign features like favicons can become attack vectors when not properly secured. Organizations should also consider implementing user education programs to raise awareness about the risks of visiting untrusted websites and the importance of keeping software updated.