CVE-2006-6970 in Web Browser
Summary
by MITRE
Opera 9.10 Final allows remote attackers to bypass the Fraud Protection mechanism by adding certain characters to the end of a domain name, as demonstrated by the "." and "/" characters, which is not caught by the blacklist filter.
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Analysis
by VulDB Data Team • 10/10/2017
The vulnerability identified as CVE-2006-6970 represents a significant security flaw in Opera 9.10 Final's fraud protection mechanism, specifically targeting the browser's domain validation and blacklist filtering system. This weakness allows malicious actors to circumvent security measures designed to protect users from phishing and fraudulent websites by exploiting a subtle but critical oversight in how domain names are processed and validated.
The technical flaw manifests through a specific method of domain name manipulation where attackers can append certain characters such as the period "." and forward slash "/" to the end of domain names to bypass the blacklist filter. This occurs because the browser's fraud protection system fails to properly sanitize or normalize domain names before checking against its blacklist database. The vulnerability stems from inadequate input validation and domain name parsing logic that does not account for these specific character sequences that could alter the domain resolution process while remaining undetected by the security filters.
This flaw operates at the intersection of web browser security and domain validation protocols, creating a pathway for attackers to potentially access fraudulent websites that would normally be blocked by the browser's built-in protection mechanisms. The operational impact extends beyond simple bypass of security measures as it undermines user trust in the browser's fraud protection system, potentially exposing users to phishing attacks, malware distribution, and other malicious activities that rely on domain name manipulation to deceive users.
The vulnerability aligns with CWE-170, which addresses improper handling of string termination and null characters, and demonstrates how seemingly minor input validation gaps can create significant security risks. From an ATT&CK perspective, this flaw maps to T1566.001 - Phishing: Spearphishing Attachment, as it enables attackers to craft domain names that appear legitimate while bypassing security controls. The issue also relates to T1071.004 - Application Layer Protocol: DNS, as it exploits weaknesses in how domain names are processed during DNS resolution and validation.
The implications of this vulnerability extend to the broader context of web browser security architecture, where proper input sanitization and domain name normalization are critical components of fraud protection systems. Organizations and users relying on Opera 9.10 Final would be exposed to increased risk of falling victim to sophisticated phishing attacks that leverage this specific bypass technique. The vulnerability highlights the importance of comprehensive testing of security filters against edge cases and the necessity of robust input validation mechanisms that account for all possible character combinations and their potential impact on security controls.
Mitigation strategies should focus on implementing proper domain name normalization and validation before blacklist checks, ensuring that all domain name variations are properly processed and that character sequences are handled consistently regardless of their position in the domain name. Browser vendors should also consider implementing more comprehensive character filtering and validation rules that account for all potential bypass techniques, while maintaining compatibility with legitimate domain name structures. Regular security updates and patches should address such validation gaps promptly to prevent exploitation of similar vulnerabilities in the broader browser ecosystem.