CVE-2004-1451 in Mozilla
Summary
by MITRE
Mozilla before 1.6 does not display the entire URL in the status bar when a link contains %00, which could allow remote attackers to trick users into clicking on unknown or untrusted sites and facilitate phishing attacks.
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Analysis
by VulDB Data Team • 03/13/2017
The vulnerability described in CVE-2004-1451 represents a critical user interface deception flaw in the Mozilla browser series prior to version 1.6. This issue stems from improper URL handling and display mechanisms within the browser's status bar functionality. When a hyperlink contains a null byte character represented as %00 in the URL encoding, the browser fails to render the complete URL in the status bar, instead truncating it at the point where the null byte appears. This truncation creates a misleading display that obscures the true destination of the link, enabling malicious actors to craft deceptive URLs that appear legitimate while actually directing users to harmful destinations.
The technical implementation of this vulnerability involves the browser's URL parsing and rendering pipeline where null bytes are processed as string terminators rather than valid URL characters. When the Mozilla browser encounters a URL containing %00, it treats this character as a string terminator during status bar display operations, causing the display to cut off at that point. This behavior violates the expected URL handling standards and creates a significant security gap in user awareness mechanisms. The vulnerability specifically affects the browser's ability to properly sanitize and display URL information, which is a fundamental security feature designed to protect users from malicious web content.
The operational impact of this vulnerability extends beyond simple phishing attacks to encompass broader security implications for user trust and browser security posture. Attackers can exploit this flaw by crafting links that appear to point to trusted domains while actually redirecting to malicious sites. The truncated URL display makes it extremely difficult for users to verify the actual destination of links, particularly when the malicious component appears after the null byte. This vulnerability directly relates to attack techniques categorized under the MITRE ATT&CK framework in the T1566 phase, specifically targeting the 'Phishing' tactic where adversaries attempt to trick users into clicking on malicious links. The flaw enables attackers to bypass user verification mechanisms that rely on status bar URL display as a security control.
From a security standards perspective, this vulnerability aligns with CWE-1230, which addresses issues related to improper handling of special characters in URLs, and CWE-20, which covers the general category of improper input validation. The flaw demonstrates inadequate input sanitization and display handling in the browser's user interface components. Organizations and users affected by this vulnerability face significant risks as the deception mechanism operates at the user interaction level, making it particularly dangerous for social engineering attacks. The security implications extend to enterprise environments where users may be less vigilant about URL verification, potentially leading to successful phishing campaigns that would otherwise be detected through normal URL inspection practices.
The recommended mitigation strategies for this vulnerability include immediate upgrade to Mozilla Firefox version 1.6 or later, which contains the necessary fixes to properly handle null byte characters in URLs. Additionally, users should implement enhanced browser security configurations that include URL validation checks and status bar display enhancements. Security administrators should consider implementing additional network-level protections such as URL filtering and content inspection systems that can detect and block suspicious URL patterns containing null bytes. The fix implemented in Mozilla version 1.6 involved modifying the URL parsing and display logic to properly handle null byte characters without truncating the URL display, thereby restoring the intended security mechanism that allows users to verify link destinations. This vulnerability serves as a reminder of the critical importance of proper input validation and user interface security in web browsers, particularly when dealing with special characters that may have different interpretations across various system components.