CVE-2007-0981 in Firefox
Summary
by MITRE
Mozilla based browsers, including Firefox before 1.5.0.10 and 2.x before 2.0.0.2, and SeaMonkey before 1.0.8, allow remote attackers to bypass the same origin policy, steal cookies, and conduct other attacks by writing a URI with a null byte to the hostname (location.hostname) DOM property, due to interactions with DNS resolver code.
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Analysis
by VulDB Data Team • 01/12/2025
This vulnerability represents a critical security flaw in mozilla-based web browsers that fundamentally undermines the core security principle of same origin policy enforcement. The issue stems from how browsers handle URI parsing and DNS resolution when null bytes are present in hostname values, creating a pathway for malicious actors to circumvent security boundaries that protect user data and prevent cross-site attacks. The vulnerability affects a wide range of browser versions including firefox 1.5.0.10 and earlier, firefox 2.x versions before 2.0.0.2, and seamonkey browsers before 1.0.8, indicating a widespread impact across multiple browser implementations that share common underlying codebases.
The technical mechanism behind this vulnerability involves the manipulation of the location.hostname DOM property through URI strings containing null bytes, which creates a mismatch between how the browser parses and resolves hostnames internally versus how it enforces security policies. When a null byte is embedded in a URI's hostname portion, the DNS resolver code interacts with the browser's security mechanisms in an unexpected way, allowing attackers to inject malicious content or manipulate the browser's security context. This particular flaw falls under the category of input validation and sanitization issues, specifically aligning with CWE-170 which addresses improper handling of null bytes in input processing. The vulnerability demonstrates how seemingly innocuous character handling can create significant security implications when combined with DNS resolution logic and browser security enforcement mechanisms.
The operational impact of this vulnerability extends far beyond simple privilege escalation, as it enables sophisticated attack vectors including session hijacking, cookie theft, and cross-site scripting attacks that can compromise user sessions and personal data. Attackers can exploit this weakness to bypass the same origin policy that prevents scripts from one domain from accessing resources from another domain, effectively allowing malicious code to read sensitive cookies and session information from different origins. This creates opportunities for man-in-the-middle attacks, credential theft, and data exfiltration that could compromise user accounts and sensitive information. The vulnerability particularly affects web applications that rely on browser security boundaries for protection, making it a serious concern for any organization running affected browser versions. According to ATT&CK framework, this vulnerability maps to T1071.004 for application layer protocol and T1566 for credential access, demonstrating both network protocol manipulation and credential theft capabilities.
Mitigation strategies for this vulnerability require immediate patching of affected browser versions, as the flaw exists at the core browser implementation level and cannot be effectively addressed through client-side code changes alone. Organizations should prioritize updating all affected browsers to their patched versions, which include firefox 1.5.0.10 and 2.0.0.2, and seamonkey 1.0.8, respectively, to ensure proper null byte handling in URI parsing and DNS resolution. Network administrators should implement additional monitoring for suspicious URI patterns and null byte usage in web traffic, while security teams should review existing browser security policies and consider implementing additional protections such as strict content security policies to limit the impact of potential exploitation. The vulnerability also highlights the importance of comprehensive input validation in security-critical applications and the need for thorough testing of edge cases involving special characters in URL handling.