CVE-2012-3693 in iOS
Summary
by MITRE
Incomplete blacklist vulnerability in WebKit in Apple Safari before 6.0 allows remote attackers to spoof domain names in URLs, and possibly conduct phishing attacks, by leveraging the availability of IDN support and Unicode fonts to construct unspecified homoglyphs.
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Analysis
by VulDB Data Team • 01/04/2025
The vulnerability identified as CVE-2012-3693 represents a critical security flaw in Apple Safari's WebKit rendering engine that existed prior to version 6.0. This issue stems from an incomplete blacklist implementation that fails to properly validate internationalized domain names, creating a significant attack surface for malicious actors seeking to exploit user trust through deceptive web navigation. The vulnerability specifically leverages the browser's support for internationalized domain names and Unicode font rendering capabilities to construct domain names that appear visually identical to legitimate sites while actually resolving to different IP addresses or servers. This creates a dangerous scenario where users cannot reliably distinguish between authentic and malicious websites through visual inspection alone.
The technical nature of this vulnerability resides in the browser's insufficient filtering mechanism for handling Unicode characters in domain name resolution. When Safari processes domain names containing internationalized characters, the browser's validation system fails to adequately block potentially malicious homoglyphs that exploit the visual similarity of characters from different Unicode scripts. This allows attackers to register domain names that contain characters visually indistinguishable from those in legitimate domains, effectively creating a form of domain name confusion that bypasses traditional security measures. The flaw operates at the protocol level where domain name validation should occur, specifically in the handling of Internationalized Domain Names in Applications (IDNA) standards and the subsequent rendering of these names in the browser's address bar.
The operational impact of CVE-2012-3693 extends far beyond simple visual deception, creating substantial risks for user authentication and security awareness. Attackers can exploit this vulnerability to craft phishing sites that appear legitimate to users who may not notice the subtle differences in character encoding between the displayed URL and the actual domain. This vulnerability directly aligns with attack patterns described in the MITRE ATT&CK framework under the technique of credential access through social engineering and deception. The ability to spoof domain names in URLs provides attackers with a powerful vector for conducting sophisticated phishing campaigns where victims may be misled into believing they are visiting trusted websites, potentially leading to credential theft, financial fraud, or malware installation. The vulnerability affects all users who rely on Safari's address bar for domain verification, making it particularly dangerous in enterprise environments where users may be less security-aware.
This vulnerability demonstrates a failure in implementing proper input validation and domain name sanitization that should have been addressed through adherence to established security standards such as those outlined in the CWE catalog under CWE-174, which addresses weaknesses in input validation for Unicode characters. The incomplete blacklist approach represents a classic security anti-pattern where insufficient validation allows malicious inputs to bypass security controls. Organizations should implement comprehensive mitigations including immediate browser updates to versions that address the vulnerability, deployment of additional URL filtering solutions, and user education about the risks of visual domain spoofing. The security community should also consider the broader implications of Unicode handling in web applications and the importance of implementing robust character validation and sanitization techniques that prevent such homoglyph-based attacks. Network administrators should monitor for suspicious domain registrations that may exploit this vulnerability and implement additional layers of security such as DNS-based filtering and browser security extensions to protect users from these sophisticated attacks.