CVE-2012-1940 in Firefox
Summary
by MITRE
Use-after-free vulnerability in the nsFrameList::FirstChild function in Mozilla Firefox 4.x through 12.0, Firefox ESR 10.x before 10.0.5, Thunderbird 5.0 through 12.0, Thunderbird ESR 10.x before 10.0.5, and SeaMonkey before 2.10 allows remote attackers to execute arbitrary code or cause a denial of service (heap memory corruption and application crash) by changing the size of a container of absolutely positioned elements in a column.
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Analysis
by VulDB Data Team • 10/21/2024
The CVE-2012-1940 vulnerability represents a critical use-after-free flaw within the Mozilla Firefox browser ecosystem affecting multiple products including Firefox versions 4.0 through 12.0, Firefox ESR 10.x before 10.0.5, Thunderbird versions 5.0 through 12.0, Thunderbird ESR 10.x before 10.0.5, and SeaMonkey before 2.10. This vulnerability resides in the nsFrameList::FirstChild function which is responsible for managing frame list structures in the browser's rendering engine. The flaw occurs when handling absolutely positioned elements within column containers, creating a scenario where freed memory can be accessed after the original allocation has been released, leading to potential code execution or system instability.
The technical implementation of this vulnerability stems from improper memory management within the browser's layout engine, specifically when processing CSS column layouts with absolutely positioned elements. When the size of a container holding these elements is modified, the system fails to properly track the lifecycle of memory allocated for frame list structures. This creates a window where the memory location may be deallocated and potentially reallocated for other purposes, yet the application continues to reference the freed memory location in the nsFrameList::FirstChild function. The vulnerability is classified under CWE-416 as a use-after-free condition, which is a well-known class of memory safety issues that can be exploited for arbitrary code execution. The attack vector requires a remote attacker to craft malicious web content that triggers the specific CSS layout scenario, making this a remote code execution vulnerability with significant impact potential.
The operational impact of this vulnerability extends beyond simple application crashes to encompass full remote code execution capabilities. When exploited, the heap memory corruption can be leveraged to execute arbitrary code with the privileges of the affected application, potentially allowing attackers to gain complete control over the victim's system. The vulnerability affects multiple Mozilla products simultaneously, amplifying its potential impact across different user bases. The specific conditions required for exploitation involve manipulating CSS column layouts with absolutely positioned elements, which are common web design patterns, making the attack surface relatively broad. Security researchers have noted that this vulnerability can be particularly dangerous because it can be triggered through standard web browsing activities without requiring user interaction beyond visiting a malicious website, making it a prime target for drive-by download attacks.
Mitigation strategies for CVE-2012-1940 focus on immediate patch application and browser updates as the primary defense mechanism. Organizations should prioritize updating all affected Mozilla products to their latest secure versions, particularly since this vulnerability affects both regular and extended support releases. Browser vendors have implemented various memory safety improvements in subsequent versions, including enhanced memory deallocation tracking and improved frame list management. Additionally, implementing security measures such as address space layout randomization, data execution prevention, and sandboxing can provide additional protection layers against exploitation attempts. Network-level defenses including web application firewalls and content filtering systems can help detect and block malicious content that might trigger this vulnerability. The ATT&CK framework categorizes this vulnerability under the T1059 technique for execution through web-based attacks, highlighting the importance of maintaining current security patches and implementing layered defense strategies. System administrators should also consider monitoring for unusual memory access patterns or application crashes that might indicate exploitation attempts, while security teams should maintain awareness of related vulnerabilities in the same codebase that might provide alternative attack vectors.