CVE-2005-0235 in Web Browser
Summary
by MITRE
The International Domain Name (IDN) support in Opera 7.54 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-2005-0235 represents a significant security flaw in Opera 7.54's handling of International Domain Name support, specifically exposing users to sophisticated phishing attacks through carefully crafted domain name spoofing techniques. This issue stems from the browser's improper handling of punycode encoding, a standard that allows international domain names to be represented using the standard ascii character set. The vulnerability creates a dangerous mismatch between how domain names appear to users in URLs and how they are actually processed by the browser's SSL certificate verification system. When attackers utilize homograph characters from different character sets such as cyrillic or arabic scripts, they can create domain names that visually appear identical or nearly identical to legitimate domains while being technically distinct, thus enabling malicious actors to deceive users into trusting fraudulent websites.
The technical implementation flaw lies in Opera's inconsistent handling of character encoding between URL display and SSL certificate validation processes. When a user encounters a punycode encoded domain name in a URL, the browser displays it in a human-readable format that may contain characters from different scripts that visually resemble the original domain. However, the SSL certificate validation process continues to use the underlying punycode representation, creating a scenario where the visual representation of the domain name in the address bar can be deceivingly similar to a legitimate domain. This inconsistency creates a critical gap in the browser's security model that attackers can exploit by registering domain names that use homograph characters to create visually identical representations to well-known legitimate domains, making it extremely difficult for users to distinguish between genuine and malicious sites.
The operational impact of this vulnerability extends far beyond simple phishing attacks, as it fundamentally undermines user trust in the browser's security mechanisms and creates a persistent threat vector that can be exploited across multiple attack scenarios. Users who rely on visual domain name recognition for security purposes become vulnerable to sophisticated social engineering attacks where the attacker's domain name appears authentic in the browser's address bar while the underlying SSL certificate validation processes operate on different character representations. This vulnerability particularly affects users who may not be technically savvy and rely heavily on visual cues to identify legitimate websites, making it a significant concern for enterprise environments where users may encounter such attacks during routine web browsing activities. The attack surface is further expanded because this vulnerability can be leveraged across multiple protocols and services that rely on domain name verification for security purposes.
The security implications of this vulnerability align with several established frameworks including CWE-1004 which addresses insecure default permissions and CWE-200 which covers information exposure through improper error handling. From an ATT&CK framework perspective, this vulnerability maps to techniques such as T1566 for phishing attacks and T1071 for application layer protocol usage, specifically targeting the user trust model that browsers establish. The vulnerability also represents a failure in the principle of least privilege as the browser does not properly enforce consistent character representation validation across different security contexts. Organizations should implement immediate mitigations including browser updates to versions that properly handle IDN character encoding, user education about recognizing potentially suspicious domain names, and network-level monitoring for suspicious domain name patterns. Additionally, implementing proper SSL certificate validation procedures that enforce consistent character representation across all security contexts would provide additional defense against similar vulnerabilities in the future.