CVE-2005-0236 in OmniWeb
Summary
by MITRE
The International Domain Name (IDN) support in Omniweb 5 allows remote attackers to spoof domain names using punycode encoded domain names that are decoded in URLs and SSL certificates in a way that uses homograph characters from other character sets, which facilitates phishing attacks.
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Analysis
by VulDB Data Team • 06/20/2024
The vulnerability described in CVE-2005-0236 represents a critical security flaw in Omniweb 5's handling of International Domain Name support, specifically exposing users to sophisticated phishing attacks through deceptive domain name encoding techniques. This issue stems from the browser's inadequate processing of punycode encoded domain names, which are designed to represent non-ASCII characters using only ASCII characters for internet domain name registration. The flaw occurs when the browser decodes these punycode representations in URLs and SSL certificates, allowing malicious actors to create domain names that appear identical or visually similar to legitimate ones but contain characters from different character sets that are indistinguishable to the human eye.
The technical implementation of this vulnerability involves the browser's failure to properly validate and display domain names that contain homograph characters, which are characters from different character sets that look visually identical or nearly identical. When a user encounters a URL or SSL certificate containing such a domain name, the browser displays the decoded version that uses these homograph characters, creating an illusion of legitimacy while actually directing users to malicious sites. This issue directly relates to CWE-1004, which addresses insufficient user interface validation of input, and specifically targets the weakness of inadequate handling of internationalized domain names in web browsers.
The operational impact of this vulnerability is severe and directly enables phishing attacks that can bypass traditional security measures relying on visual domain name verification. Attackers can register domain names that appear identical to well-known legitimate domains but contain subtle differences in character encoding that are invisible to users. This makes it extremely difficult for end users to distinguish between legitimate and malicious websites, particularly when SSL certificates are involved since the certificate validation process fails to properly flag these deceptive domain names. The vulnerability essentially undermines the fundamental security principle of domain name verification that users rely upon for safe navigation.
Mitigation strategies for this vulnerability must address both the browser's handling of internationalized domain names and user education about potential deception techniques. Organizations should ensure that Omniweb 5 is either updated to a version that properly handles punycode encoding or replaced with a modern browser that implements proper IDN validation mechanisms. The recommended approach includes implementing strict validation of domain names against known malicious patterns and ensuring that browsers properly display the underlying punycode representation alongside the decoded version. Additionally, security awareness training should emphasize that visual similarity in domain names does not guarantee legitimacy, particularly when dealing with internationalized domain names that may contain homograph characters. This vulnerability demonstrates the importance of following security standards such as those outlined in the IETF's RFC 3490 and RFC 3492 specifications for internationalized domain name handling and underscores the need for robust input validation and display mechanisms in web browsers.