CVE-2008-4065 in Firefox
Summary
by MITRE
Mozilla Firefox before 2.0.0.17 and 3.x before 3.0.2, Thunderbird before 2.0.0.17, and SeaMonkey before 1.1.12 allow remote attackers to bypass cross-site scripting (XSS) protection mechanisms and conduct XSS attacks via byte order mark (BOM) characters that are removed from JavaScript code before execution, aka "Stripped BOM characters bug."
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Analysis
by VulDB Data Team • 08/17/2019
The vulnerability described in CVE-2008-4065 represents a critical flaw in the web browser security architecture of Mozilla Firefox, Thunderbird, and SeaMonkey applications. This issue stems from the improper handling of byte order mark characters within JavaScript code execution contexts, specifically when these characters are stripped from code before processing. The vulnerability affects versions prior to Firefox 2.0.0.17 and 3.x 3.0.2, Thunderbird 2.0.0.17, and SeaMonkey 1.1.12, creating a significant security gap that adversaries could exploit to circumvent built-in cross-site scripting protection mechanisms. The root cause lies in how the browser's JavaScript engine processes and sanitizes input data, particularly when byte order mark characters are present in script content.
The technical exploitation of this vulnerability occurs through the manipulation of byte order mark characters within JavaScript code that is intended to be executed. When these BOM characters are removed from JavaScript code before execution, they can be strategically positioned to bypass security checks that would normally prevent malicious script injection. This creates a scenario where attackers can embed malicious code within seemingly benign JavaScript that appears to be properly sanitized. The vulnerability operates at the intersection of input validation and code execution phases, where the stripping process inadvertently removes protective mechanisms while leaving the malicious payload intact. This flaw specifically targets the browser's security model that relies on proper character handling to prevent XSS attacks.
The operational impact of this vulnerability is substantial as it allows remote attackers to execute arbitrary JavaScript code within the context of the victim's browser session. This can lead to session hijacking, credential theft, data exfiltration, and the execution of malicious commands on affected systems. The bypass of XSS protection mechanisms means that users who visit compromised websites or receive malicious email content could have their browsers exploited without their knowledge. The vulnerability is particularly dangerous because it operates silently in the background, allowing attackers to establish persistent access to user sessions and potentially escalate privileges within the browser environment.
Security mitigations for this vulnerability include immediate updates to affected software versions where the BOM character handling has been corrected. Organizations should implement comprehensive patch management strategies to ensure all affected browsers and email clients are updated promptly. Network administrators should consider implementing web application firewalls and content filtering solutions that can detect and block suspicious JavaScript patterns. The vulnerability aligns with CWE-79 which describes cross-site scripting flaws, and relates to ATT&CK technique T1059.007 for scripting languages. Additional protective measures include browser hardening configurations, strict content security policies, and user education about avoiding suspicious websites and email attachments. Security teams should monitor for indicators of compromise related to this vulnerability and implement proper logging to detect potential exploitation attempts.