CVE-2004-0537 in Web Browser
Summary
by MITRE
Opera 7.50 and earlier allows remote web sites to provide a "Shortcut Icon" (favicon) that is wider than expected, which could allow the web sites to spoof a trusted domain and facilitate phishing attacks using a wide icon and extra spaces.
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Analysis
by VulDB Data Team • 03/09/2021
The vulnerability described in CVE-2004-0537 represents a significant security flaw in Opera web browser versions 7.50 and earlier that enables malicious actors to craft deceptive favicon images capable of facilitating sophisticated phishing attacks. This issue stems from the browser's inadequate handling of icon dimensions during the favicon loading process, specifically when processing shortcut icons that exceed normal expected width parameters. The flaw allows remote websites to serve favicon images that are disproportionately wide, creating visual deception that can mislead users into believing they are visiting legitimate trusted domains.
The technical implementation of this vulnerability exploits the browser's rendering engine's failure to properly validate and constrain favicon dimensions during the display process. When Opera encounters a favicon that exceeds the expected width parameters, the browser fails to implement proper boundary checks that would normally prevent such oversized icons from being displayed in a manner that could confuse users. This inadequate validation creates a window where attackers can craft favicon images that, when displayed alongside legitimate domain names, can create visual confusion through the use of wide icons combined with extra spacing techniques. The vulnerability specifically targets the browser's user interface elements that display domain information and favicon representations simultaneously, making it particularly dangerous for phishing operations.
The operational impact of this vulnerability extends beyond simple visual deception to create real security risks for end users who may be tricked into believing they are visiting legitimate websites. Attackers can exploit this flaw by creating favicon images that, when combined with extra spacing and wide dimensions, can make malicious websites appear to display trusted domain information in a way that closely mimics legitimate sites. This capability directly supports phishing attack vectors by enabling attackers to create more convincing deceptive interfaces that can bypass user suspicion mechanisms. The vulnerability is particularly concerning because it operates at the user interface level where users naturally expect to see consistent and trustworthy visual indicators of website authenticity. According to CWE standards, this represents a weakness in input validation and user interface security controls, specifically categorized under CWE-20 Input Validation and CWE-611 Improper Restriction of XML External Entity Reference. The attack pattern aligns with ATT&CK technique T1566.001 Phishing using email and T1531 Account Access Removal, as it enables more effective phishing campaigns that can compromise user trust and potentially lead to credential theft.
Mitigation strategies for this vulnerability require immediate browser updates to versions that properly validate and constrain favicon dimensions during the display process. Security professionals should implement network-level controls to monitor and block suspicious favicon content, while also educating users about the importance of verifying website authenticity through multiple means beyond favicon appearance. Browser vendors should ensure proper input validation and boundary checking for all icon and image loading operations to prevent similar issues in future implementations. Additionally, organizations should consider implementing security policies that require regular browser updates and maintain awareness of known vulnerabilities that could be exploited through user interface manipulation techniques. The vulnerability demonstrates the critical importance of proper input validation and boundary checking in user interface components, as it shows how seemingly minor display flaws can create significant security risks through social engineering exploitation.