CVE-2007-3285 in Firefox
Summary
by MITRE
Mozilla Firefox before 2.0.0.5, when run on Windows, allows remote attackers to bypass file type checks and possibly execute programs via a (1) file:/// or (2) resource: URI with a dangerous extension, followed by a NULL byte (%00) and a safer extension, which causes Firefox to treat the requested file differently than Windows would.
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Analysis
by VulDB Data Team • 07/23/2019
This vulnerability exists in mozilla firefox versions prior to 2.0.0.5 when operating on windows platforms and represents a significant security flaw that undermines the browser's file type validation mechanisms. The issue stems from how firefox processes uri references containing specific file extensions combined with null byte sequences, creating a condition where the browser's interpretation of file types diverges from windows operating system behavior. This discrepancy allows attackers to craft malicious file references that appear harmless to the operating system while being interpreted as executable by the browser. The vulnerability specifically targets the way firefox handles file type checking when processing file:/// and resource: uri schemes, which are fundamental components of web browser security architecture.
The technical exploitation of this vulnerability relies on a sophisticated manipulation of file path handling and null byte injection techniques. Attackers can construct malicious uri references where a dangerous file extension is followed by a null byte sequence and then a seemingly safe extension, effectively bypassing firefox's built-in file type validation controls. This technique exploits a fundamental mismatch between how firefox processes and validates file extensions versus how windows handles the same file references. The null byte injection causes firefox to truncate the uri at the null character, interpreting only the initial extension while windows continues processing the complete path including the malicious extension. This represents a classic case of input validation bypass where the browser's security controls fail to properly sanitize uri parameters before file access operations.
The operational impact of this vulnerability is severe as it allows remote attackers to potentially execute arbitrary programs on vulnerable systems without user interaction. When firefox processes these crafted uri references, it may attempt to execute files that would normally be blocked by windows security controls due to their dangerous extensions. The vulnerability essentially creates a pathway for attackers to circumvent the operating system's file execution restrictions, enabling code execution through browser-based attacks. This type of vulnerability can be leveraged in phishing campaigns, drive-by download scenarios, or social engineering attacks where users might inadvertently trigger malicious code execution simply by visiting compromised web pages or clicking on malicious links. The attack vector is particularly dangerous because it operates at the intersection of browser security and operating system security controls.
This vulnerability maps directly to CWE-174, which describes "Dangerous Functions" and specifically relates to the improper handling of file paths and extension validation. The flaw also aligns with ATT&CK technique T1059.007 for "Command and Scripting Interpreter: JavaScript' and T1203 for "Exploitation for Client Execution" in the enterprise attack framework. The root cause of this issue demonstrates poor input sanitization and inadequate validation of uri parameters, particularly in how the browser handles null byte sequences in file references. Security professionals should note that this vulnerability highlights the importance of consistent security controls across different system layers, as the browser's interpretation of file references should align with the operating system's security policies. The vulnerability also demonstrates the critical need for proper null byte handling in web applications and browser implementations to prevent such bypass scenarios.
Organizations should implement immediate mitigations including upgrading to firefox version 2.0.0.5 or later, which contains the necessary patches to address this file type validation issue. Network administrators should consider implementing additional security controls such as web application firewalls that can detect and block suspicious uri patterns, particularly those containing null byte sequences or unusual extension combinations. Browser security policies should be reviewed to ensure that file type validation is consistent across different uri schemes and that proper input sanitization is implemented. Additionally, user education programs should emphasize the importance of avoiding suspicious web content and understanding the potential risks associated with visiting untrusted websites. The vulnerability underscores the need for comprehensive security testing that includes cross-platform validation scenarios where browser behavior might differ from operating system security controls.