CVE-2012-3966 in Firefox
Summary
by MITRE
Mozilla Firefox before 15.0, Firefox ESR 10.x before 10.0.7, Thunderbird before 15.0, Thunderbird ESR 10.x before 10.0.7, and SeaMonkey before 2.12 allow remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a negative height value in a BMP image within a .ICO file, related to (1) improper handling of the transparency bitmask by the nsICODecoder component and (2) improper processing of the alpha channel by the nsBMPDecoder component.
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Analysis
by VulDB Data Team • 10/22/2024
The vulnerability described in CVE-2012-3966 represents a critical memory corruption flaw affecting multiple Mozilla products including Firefox, Thunderbird, and SeaMonkey. This vulnerability stems from improper handling of image file formats during the decoding process, specifically when processing BMP images embedded within ICO files. The flaw manifests when the system encounters a negative height value in a BMP image, which triggers unpredictable behavior in the image processing components. The issue affects versions prior to Firefox 15.0, Firefox ESR 10.x before 10.0.7, Thunderbird 15.0, Thunderbird ESR 10.x before 10.0.7, and SeaMonkey 2.12, indicating a widespread impact across the Mozilla ecosystem.
The technical implementation of this vulnerability involves two distinct but related components within the Mozilla rendering engine. The nsICODecoder component fails to properly handle transparency bitmasks when processing ICO files containing BMP images with negative height values, while the nsBMPDecoder component incorrectly processes alpha channel information in similar scenarios. This dual-component failure creates a memory corruption condition that can be exploited by remote attackers to execute arbitrary code on vulnerable systems. The vulnerability falls under CWE-125, which describes out-of-bounds read conditions, and CWE-787, which covers out-of-bounds write vulnerabilities, both of which are common in image processing libraries where buffer boundaries are not properly validated.
From an operational perspective, this vulnerability presents a significant risk to organizations relying on Mozilla-based applications for email and web browsing. Attackers can craft malicious ICO files containing specially formatted BMP images with negative height values to exploit the memory corruption issue. The attack vector is particularly dangerous because it can be delivered through email attachments or web content, making it difficult to prevent through traditional network security measures. Successful exploitation can result in complete system compromise, denial of service, or data exfiltration, depending on the attacker's intent and the specific environment. The vulnerability aligns with ATT&CK technique T1203, which covers exploitation of remote services, and T1059, covering command and scripting interpreters, as attackers may leverage the arbitrary code execution capability for further system compromise.
The mitigation strategy for CVE-2012-3966 involves immediate patching of all affected Mozilla products to versions that properly handle negative height values in BMP images. Organizations should implement comprehensive patch management processes to ensure all systems are updated promptly, as the vulnerability can be exploited remotely without user interaction. Additional defensive measures include implementing strict content filtering for email attachments and web downloads, particularly for image files, and monitoring network traffic for suspicious ICO file transfers. Security teams should also consider deploying application whitelisting solutions to restrict execution of untrusted image processing components and maintain detailed monitoring of system logs for signs of exploitation attempts. The vulnerability highlights the importance of proper input validation in multimedia processing libraries and demonstrates how seemingly benign image format handling can become a critical security concern when not properly secured against malformed input data.