CVE-2013-1699 in Firefox
Summary
by MITRE
The Internationalized Domain Name (IDN) display algorithm in Mozilla Firefox before 22.0 does not properly handle the .com, .name, and .net top-level domains, which allows remote attackers to spoof the address bar via unspecified homograph characters.
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Analysis
by VulDB Data Team • 05/17/2021
The vulnerability identified as CVE-2013-1699 represents a critical security flaw in Mozilla Firefox's handling of internationalized domain names within the address bar display mechanism. This issue specifically affects Firefox versions prior to 22.0 and stems from the browser's inadequate implementation of the IDN display algorithm for certain top-level domains including .com, .name, and .net. The flaw enables attackers to exploit homograph characters that appear visually identical or nearly identical to legitimate domain characters, creating deceptive URLs that can mislead users into believing they are visiting trusted websites when they are actually navigating to malicious alternatives.
The technical nature of this vulnerability resides in the browser's failure to properly normalize and display internationalized domain names according to established standards while maintaining visual distinction between legitimate and spoofed characters. When users encounter domain names containing homograph characters, Firefox's display algorithm does not adequately differentiate between standard ASCII characters and their Unicode counterparts that may appear visually identical. This creates an attack surface where malicious actors can register domains using Unicode characters that visually resemble the legitimate .com, .name, or .net TLDs, making it extremely difficult for users to distinguish between authentic and fraudulent websites through visual inspection alone.
The operational impact of this vulnerability extends beyond simple phishing attacks, as it fundamentally undermines user trust in the browser's address bar security indicators. Users who rely on visual verification of website addresses become vulnerable to sophisticated social engineering attacks where attackers can craft URLs that appear legitimate at first glance. This vulnerability particularly affects users who browse the internet without relying on additional security measures such as SSL certificate validation warnings or security software that might flag suspicious domains. The attack vector involves remote exploitation through web content delivery, where users can be redirected to malicious sites through compromised web pages or malicious advertisements that contain the spoofed domain names.
This vulnerability aligns with CWE-1004, which addresses insecure default settings in security-critical applications, and specifically relates to CWE-345, which covers insufficient verification of data authenticity. The flaw demonstrates a failure in the principle of least privilege and trust verification within the browser's security architecture. From an ATT&CK framework perspective, this vulnerability maps to techniques involving social engineering and credential access through deceptive user interfaces, specifically falling under T1566 for credential access and T1531 for tampering with security software. The attack chain typically involves initial compromise through web browsing, followed by user deception through visually convincing but malicious domain names that bypass traditional security controls.
Organizations and individuals should immediately upgrade to Firefox 22.0 or later versions to remediate this vulnerability, as the fix implemented by Mozilla includes enhanced IDN display algorithms that properly handle character normalization and visual distinction. Additional mitigations include implementing browser security extensions that provide enhanced URL verification, enabling security software that can detect and block suspicious domain registrations, and conducting user education on recognizing potential phishing attempts beyond simple visual inspection. Network administrators should also consider implementing DNS security measures and web filtering solutions that can detect and block known malicious domains that exploit this vulnerability. The remediation process should include comprehensive testing to ensure that the updated browser correctly handles internationalized domain names while maintaining compatibility with legitimate internationalized websites.