CVE-2007-1762 in Firefox
Summary
by MITRE
Mozilla Firefox 2.0.0.1 through 2.0.0.3 does not canonicalize URLs before checking them against the phishing site blacklist, which allows remote attackers to bypass phishing protection via multiple / (slash) characters in the URL.
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Analysis
by VulDB Data Team • 08/28/2018
The vulnerability described in CVE-2007-1762 represents a significant flaw in Mozilla Firefox's security architecture that specifically targeted the browser's anti-phishing protection mechanisms. This issue affected Firefox versions 2.0.0.1 through 2.0.0.3, creating a pathway for malicious actors to circumvent the browser's built-in defenses against phishing attacks. The core problem lies in how Firefox processes and validates URLs before comparing them against its blacklist of known malicious sites, creating a fundamental weakness in the security validation pipeline that could be exploited by threat actors.
The technical flaw stems from Firefox's failure to properly canonicalize URLs during the phishing detection process. Canonicalization is the process of converting a URL into its standard, normalized form to ensure consistent comparison and validation. When attackers construct malicious URLs with multiple consecutive forward slash characters, the browser's phishing protection system fails to properly normalize these URLs before checking them against the blacklist database. This allows attackers to craft URLs that appear legitimate to the browser's security checks while actually pointing to malicious destinations, effectively bypassing the protection mechanisms designed to prevent users from visiting known phishing sites.
This vulnerability operates at the intersection of several security domains and can be categorized under CWE-170, which deals with improper handling of canonicalization issues. The operational impact of this flaw is particularly concerning as it directly undermines user trust in browser security features and creates a false sense of protection for users who believe they are safe from phishing attacks. Attackers could exploit this weakness by crafting URLs that contain multiple slashes in specific patterns, making the URL appear to point to a legitimate domain while actually redirecting users to malicious sites that would otherwise be blocked by the phishing protection system.
The exploitation of this vulnerability aligns with techniques found in the ATT&CK framework under the T1566 tactic, which covers social engineering attacks including phishing. The flaw enables attackers to bypass automated security controls that should prevent users from accessing known malicious sites, effectively allowing them to perform credential harvesting and other malicious activities without triggering browser warnings. This represents a critical failure in the browser's defense-in-depth strategy, where multiple layers of security should work together to prevent user exposure to dangerous websites.
Organizations and individual users affected by this vulnerability should immediately update to Firefox version 2.0.0.4 or later, which contained the necessary patches to properly canonicalize URLs before phishing protection checks. The fix implemented by Mozilla addressed the core issue by ensuring that URL normalization occurred before blacklist comparisons, eliminating the possibility of bypassing security controls through malformed URL construction. Security teams should also consider implementing additional monitoring for suspicious URL patterns and ensure that browser security updates are applied promptly across all systems to prevent exploitation of similar vulnerabilities that may exist in other software components.