CVE-2009-0652 in Firefox
Summary
by MITRE
The Internationalized Domain Names (IDN) blacklist in Mozilla Firefox 3.0.6 and other versions before 3.0.9; Thunderbird before 2.0.0.21; and SeaMonkey before 1.1.15 does not include box-drawing characters, which allows remote attackers to spoof URLs and conduct phishing attacks, as demonstrated by homoglyphs of the / (slash) and ? (question mark) characters in a subdomain of a .cn domain name, a different vulnerability than CVE-2005-0233. NOTE: some third parties claim that 3.0.6 is not affected, but much older versions perhaps are affected.
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Analysis
by VulDB Data Team • 08/28/2019
The vulnerability described in CVE-2009-0652 represents a critical security flaw in the handling of internationalized domain names within Mozilla Firefox and related applications. This issue stems from an incomplete implementation of IDN blacklists that fail to properly account for box-drawing characters, which are Unicode characters used to create visual borders and lines in text displays. The flaw allows attackers to craft deceptive domain names that appear legitimate while actually directing users to malicious sites, creating a sophisticated phishing vector that exploits the visual similarity between standard ASCII characters and Unicode box-drawing characters.
The technical implementation of this vulnerability lies in how these applications process and display internationalized domain names. When a user visits a URL containing a domain name with box-drawing characters, the browser's IDN handling mechanism fails to properly validate or sanitize these characters against known malicious patterns. Specifically, attackers can exploit homoglyphs of the forward slash / and question mark ? characters to create domain names that visually resemble legitimate sites. For instance, a malicious actor could register a domain name that appears to be a trusted website but contains box-drawing characters that make it visually indistinguishable from the real site, particularly when displayed in the browser's address bar. This vulnerability operates under CWE-1004 which categorizes insecure default security parameters, specifically related to improper input validation in internationalized domain name handling.
The operational impact of this vulnerability extends beyond simple phishing attacks to encompass a broader range of social engineering and deception techniques. Attackers can leverage this flaw to create convincing fake banking sites, e-commerce portals, or corporate intranet access points by carefully crafting domain names that appear legitimate to users who may not notice subtle visual differences. The vulnerability is particularly dangerous because it targets the fundamental trust users place in URL display mechanisms, making it difficult for end users to distinguish between legitimate and malicious websites. This type of attack maps directly to ATT&CK technique T1566.001 which involves phishing with malicious attachments, but in this case the phishing vector is through URL manipulation rather than email attachments.
The security implications of this vulnerability are compounded by the fact that it affects multiple Mozilla-based applications including Firefox, Thunderbird, and SeaMonkey across various versions. This widespread impact means that organizations and individuals using any of these applications are potentially exposed to the same deception vectors. The vulnerability's persistence across different software versions also suggests a systemic issue in the IDN handling implementation rather than a simple patchable bug. The fact that some third parties dispute the affected versions further complicates the security landscape, as it highlights the complexity of internationalized domain name security and the need for comprehensive validation across different browser implementations. Organizations should prioritize immediate patching of affected versions and consider implementing additional URL validation mechanisms as a defensive measure against this specific type of homograph attack.