CVE-2013-5601 in Firefox
Summary
by MITRE
Use-after-free vulnerability in the nsEventListenerManager::SetEventHandler function in Mozilla Firefox before 25.0, Firefox ESR 17.x before 17.0.10 and 24.x before 24.1, Thunderbird before 24.1, Thunderbird ESR 17.x before 17.0.10, and SeaMonkey before 2.22 allows remote attackers to execute arbitrary code via vectors related to a memory allocation through the garbage collection (GC) API.
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Analysis
by VulDB Data Team • 11/25/2025
The CVE-2013-5601 vulnerability represents a critical use-after-free flaw in Mozilla's browser and email client software ecosystems, specifically affecting versions prior to the mentioned security patches. This vulnerability resides within the nsEventListenerManager::SetEventHandler function, which governs how event handlers are managed in the browser's JavaScript engine. The flaw occurs when the garbage collection process fails to properly handle memory deallocation for event listener objects, creating a scenario where freed memory can be accessed and potentially overwritten by malicious code. The vulnerability is particularly dangerous because it operates within the core browser functionality that processes web content, making it an attractive target for remote exploitation.
The technical exploitation of this vulnerability involves manipulating the garbage collection API to trigger a specific memory management sequence that results in a use-after-free condition. When the SetEventHandler function processes event listeners, it may allocate memory for event handler objects and subsequently free that memory during garbage collection cycles. However, if the application continues to reference this freed memory location, particularly through JavaScript event handling mechanisms, an attacker can potentially corrupt the memory space and redirect execution flow. This type of vulnerability falls under CWE-416, which specifically addresses use-after-free conditions, and aligns with ATT&CK technique T1059.007 for script-based execution and T1059.001 for command and scripting interpreter. The vulnerability's exploitation typically requires a crafted web page that triggers the specific memory allocation and deallocation pattern necessary to create the conditions for arbitrary code execution.
The operational impact of this vulnerability extends beyond simple browser compromise, as it can lead to complete system takeover when exploited successfully. Attackers can leverage this flaw to execute malicious code with the privileges of the affected user, potentially leading to data theft, system persistence, or further network infiltration. The vulnerability affects not only Firefox but also Thunderbird and SeaMonkey products, indicating a widespread impact across Mozilla's ecosystem. Given that these applications are widely used for email and web browsing, the potential attack surface is extensive, with users potentially exposed through malicious websites or email attachments. The vulnerability's classification as a remote code execution flaw means that successful exploitation requires no local access and can occur simply by visiting a malicious webpage or opening a compromised email message.
Organizations should prioritize immediate patching of all affected versions to mitigate this vulnerability, as the window for exploitation remains open for systems running outdated software. The recommended mitigation strategy includes implementing strict update policies and maintaining current versions of all Mozilla products across enterprise environments. Security teams should also deploy network monitoring solutions to detect potential exploitation attempts and implement browser hardening measures such as disabling unnecessary JavaScript features and restricting access to potentially malicious websites. Additionally, the vulnerability highlights the importance of proper memory management practices in complex software systems and underscores the need for comprehensive code review processes to identify similar issues in other components. The ATT&CK framework suggests implementing defensive measures such as process isolation and memory protection techniques to reduce the impact of such vulnerabilities. Organizations should also consider implementing web application firewalls and content filtering solutions to prevent access to known malicious domains that may attempt to exploit this flaw. Regular security assessments and penetration testing should be conducted to identify similar memory corruption vulnerabilities that could potentially be exploited in similar ways.