CVE-2012-1939 in Firefox ESR
Summary
by MITRE
jsinfer.cpp in Mozilla Firefox ESR 10.x before 10.0.5 and Thunderbird ESR 10.x before 10.0.5 does not properly determine data types, which allows remote attackers to cause a denial of service (memory corruption and application crash) or possibly execute arbitrary code via crafted JavaScript code.
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Analysis
by VulDB Data Team • 10/21/2024
The vulnerability identified as CVE-2012-1939 resides within the jsinfer.cpp component of Mozilla Firefox ESR 10.x versions prior to 10.0.5 and Thunderbird ESR 10.x versions prior to 10.0.5. This flaw represents a critical type inference issue that affects the JavaScript engine's ability to accurately determine data types during runtime execution. The problem manifests when processing crafted JavaScript code that exploits the engine's type system, leading to unpredictable behavior that can compromise system stability and security. The vulnerability operates at the core level of the JavaScript interpreter, specifically within the type inference mechanism that is responsible for determining variable types and optimizing code execution paths.
The technical implementation of this vulnerability stems from insufficient type checking and validation within the JavaScript engine's inference system. When malicious JavaScript code is executed, the jsinfer.cpp module fails to properly validate data types, creating opportunities for memory corruption that can result in application crashes or more severe exploitation scenarios. This type of flaw falls under the CWE-129 category of Improper Validation of Array Index, as the engine's failure to properly validate type information leads to memory access violations. The vulnerability is particularly dangerous because it can be triggered through web-based attacks where remote attackers craft malicious JavaScript payloads that exploit the type inference mechanism to cause memory corruption.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially enable arbitrary code execution. When the JavaScript engine encounters malformed type information, it can lead to memory corruption that attackers might leverage to execute malicious code with the privileges of the affected application. This represents a significant threat to end-user security, as the vulnerability can be exploited through web browsers without requiring user interaction beyond visiting a malicious website. The attack surface is particularly broad given that Firefox and Thunderbird are widely deployed email clients and web browsers, making this vulnerability attractive to threat actors seeking to compromise large user bases. The vulnerability aligns with ATT&CK technique T1059.007 for Scripting and T1203 for Exploitation for Client Execution, as it enables attackers to execute code through JavaScript-based attacks.
Mitigation strategies for CVE-2012-1939 primarily focus on immediate patching of affected software versions. Organizations should prioritize updating Firefox ESR 10.x to version 10.0.5 or later and Thunderbird ESR 10.x to version 10.0.5 or later to address the underlying type inference flaw. Additionally, implementing security measures such as content security policies, sandboxing, and regular security monitoring can help reduce the risk of exploitation. Network administrators should consider deploying web application firewalls and monitoring for suspicious JavaScript activity that might indicate attempts to exploit this vulnerability. The fix implemented by Mozilla addresses the core issue in the JavaScript engine's type inference system, specifically strengthening the validation mechanisms that prevent memory corruption during type determination operations. This vulnerability serves as a reminder of the critical importance of robust type checking in interpreted languages and the potential consequences of inadequate validation in core engine components.