CVE-2012-3985 in Firefox
Summary
by MITRE
Mozilla Firefox before 16.0, Thunderbird before 16.0, and SeaMonkey before 2.13 do not properly implement the HTML5 Same Origin Policy, which allows remote attackers to conduct cross-site scripting (XSS) attacks by leveraging initial-origin access after document.domain has been set.
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Analysis
by VulDB Data Team • 04/18/2021
The vulnerability described in CVE-2012-3985 represents a critical security flaw in the implementation of the HTML5 Same Origin Policy within Mozilla Firefox versions prior to 16.0, Thunderbird versions prior to 16.0, and SeaMonkey versions prior to 2.13. This weakness stems from the improper handling of cross-origin resource sharing and document domain manipulation, creating a pathway for malicious actors to bypass fundamental web security mechanisms. The flaw specifically exploits the interaction between the document.domain property and the same origin policy enforcement, allowing attackers to escalate privileges and execute unauthorized operations across different domains.
The technical implementation of this vulnerability occurs when an attacker manipulates the document.domain property to relax origin restrictions, enabling scripts from different origins to interact more freely than intended. This manipulation creates a scenario where initial access from a trusted origin can be leveraged to perform actions that should be restricted by the same origin policy. The vulnerability is particularly dangerous because it allows attackers to bypass security boundaries that are fundamental to web browser security models, enabling them to inject malicious scripts that can access sensitive data, manipulate user sessions, or perform unauthorized actions on behalf of users. This represents a direct violation of the core security principle that different origins should be isolated from each other to prevent unauthorized access and data leakage.
The operational impact of this vulnerability extends beyond simple cross-site scripting attacks, as it fundamentally undermines the security model that web browsers rely upon to protect users from malicious websites. Attackers can exploit this flaw to conduct sophisticated attacks including session hijacking, data exfiltration, and privilege escalation within the browser environment. The vulnerability affects not just web applications but also email clients and browser-based applications that depend on proper same origin policy enforcement. This weakness creates a persistent threat vector that can be exploited across multiple applications and platforms, making it particularly dangerous for enterprise environments where users may be accessing sensitive corporate data through these vulnerable browsers.
Security mitigations for this vulnerability require immediate patching of affected browser versions to implement proper same origin policy enforcement. Organizations should prioritize updating all instances of Firefox, Thunderbird, and SeaMonkey to their patched versions, as the vulnerability cannot be effectively mitigated through configuration changes alone. The fix implemented by Mozilla addresses the specific interaction between document.domain manipulation and same origin policy enforcement, restoring proper isolation between different origins. Additionally, network administrators should monitor for exploitation attempts and implement additional security layers such as content security policies and web application firewalls to provide defense in depth. This vulnerability highlights the importance of proper security testing and validation of web standards implementation, as flaws in core security mechanisms can have widespread consequences across multiple applications and platforms.
This vulnerability aligns with CWE-346, which describes improper verification of data source, and maps to ATT&CK technique T1059.007 for script-based execution. The flaw demonstrates how browser security mechanisms can be subverted through manipulation of core web APIs, creating persistent attack vectors that can be exploited across different applications. The vulnerability serves as a reminder of the critical importance of maintaining up-to-date security implementations and proper validation of web standards across all browser implementations. Organizations should also consider implementing automated patch management systems to ensure timely deployment of security updates and reduce exposure windows to such critical vulnerabilities.