CVE-2012-4194 in Firefox
Summary
by MITRE
Mozilla Firefox before 16.0.2, Firefox ESR 10.x before 10.0.10, Thunderbird before 16.0.2, Thunderbird ESR 10.x before 10.0.10, and SeaMonkey before 2.13.2 do not prevent use of the valueOf method to shadow the location object (aka window.location), which makes it easier for remote attackers to conduct cross-site scripting (XSS) attacks via vectors involving a plugin.
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Analysis
by VulDB Data Team • 10/22/2024
This vulnerability resides in the browser security model of Mozilla Firefox and related products, specifically addressing a flaw in how the JavaScript engine handles object property access and shadowing mechanisms. The issue stems from the inability of these browsers to properly prevent the valueOf method from being used to override or shadow the location object, which creates a dangerous condition in the JavaScript execution environment. The vulnerability is particularly concerning because it allows attackers to manipulate the window.location object through the valueOf method, effectively bypassing security mechanisms designed to prevent such operations.
The technical flaw manifests when a malicious plugin or script attempts to use the valueOf method to shadow the location object, creating a scenario where the expected behavior of window.location is subverted. This shadowing allows attackers to inject malicious code that can execute within the context of the victim's browser session, leveraging the compromised location object to redirect users or execute arbitrary JavaScript commands. The vulnerability specifically affects versions prior to the mentioned patches, where the JavaScript engine failed to properly validate or restrict method overrides that could lead to privilege escalation within the browser's security boundaries.
The operational impact of this vulnerability is significant as it enables remote attackers to conduct cross-site scripting attacks with reduced complexity and increased effectiveness. Attackers can exploit this weakness by crafting malicious plugins or web content that leverages the shadowing behavior to bypass typical XSS protections. The vulnerability creates a pathway for attackers to manipulate browser navigation, steal session information, or redirect users to malicious sites without requiring additional exploitation techniques. This makes it particularly dangerous in environments where users may encounter untrusted content or plugins from unknown sources.
The vulnerability aligns with CWE-79, which describes Cross-Site Scripting flaws, and can be mapped to ATT&CK technique T1059.007 for JavaScript execution. The flaw represents a failure in input validation and object property handling within the browser's JavaScript engine, creating an attack surface that allows for privilege escalation through method overriding. Organizations should prioritize updating to the patched versions mentioned in the CVE description, as the vulnerability provides attackers with a relatively straightforward method to compromise user sessions and execute malicious code within the browser context. The security implications extend beyond simple XSS to potentially enable more sophisticated attacks including session hijacking and data exfiltration.
Mitigation strategies should include immediate deployment of the patched versions for all affected products, along with enhanced monitoring for suspicious plugin behavior or unexpected location object modifications. Security teams should also implement content security policies and regular security audits to detect potential exploitation attempts. The vulnerability demonstrates the importance of proper object property handling in browser security models and highlights the need for comprehensive testing of JavaScript engine behaviors to prevent similar shadowing attacks in the future.