CVE-2013-5602 in Firefox
Summary
by MITRE
The Worker::SetEventListener function in the Web workers implementation 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 or cause a denial of service (memory corruption) via vectors related to direct proxies.
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Analysis
by VulDB Data Team • 11/25/2025
The vulnerability identified as CVE-2013-5602 represents a critical memory corruption flaw within the Web workers implementation of Mozilla Firefox and related applications. This issue affects multiple versions of Firefox including the main release line and its extended support releases, along with Thunderbird and SeaMonkey applications. The vulnerability specifically resides in the Worker::SetEventListener function which handles event listener registration for web workers. The flaw enables remote attackers to manipulate the application's memory management through direct proxy manipulation techniques, creating a pathway for arbitrary code execution or denial of service conditions. The affected software versions span across Firefox 24.x and earlier, Firefox ESR 17.x versions prior to 17.0.10, and Thunderbird versions before 24.1, indicating a widespread impact across Mozilla's product ecosystem.
The technical exploitation of this vulnerability leverages the direct proxy mechanism within the Web workers implementation to corrupt memory structures during event listener assignment operations. When a web worker attempts to set an event listener through the Worker::SetEventListener function, the improper handling of proxy objects creates opportunities for attackers to manipulate memory pointers or overwrite critical data structures. This memory corruption can result in unpredictable behavior including application crashes, memory leaks, or more severely arbitrary code execution within the context of the vulnerable application. The direct proxy vectors suggest that attackers can manipulate proxy objects to redirect execution flow or corrupt memory layout in ways that bypass typical security mitigations. The vulnerability's classification aligns with CWE-121, which describes heap-based buffer overflow conditions, and the attack surface maps to the ATT&CK technique T1059.007 for execution through web-based interfaces. The flaw demonstrates the complexity of modern web application security where worker threads and proxy mechanisms interact in ways that can create unexpected memory access patterns.
The operational impact of CVE-2013-5602 extends beyond simple denial of service scenarios to potentially enable full system compromise when exploited. Remote attackers can leverage this vulnerability to execute arbitrary code on vulnerable systems, effectively bypassing the security boundaries that separate web content from the underlying operating system. The memory corruption nature of the flaw means that successful exploitation could lead to complete application instability or even system-level compromise depending on the execution context. Organizations using affected versions of Firefox, Thunderbird, or SeaMonkey face significant risk as this vulnerability can be triggered through standard web browsing activities without requiring any special privileges or user interaction beyond visiting malicious websites. The impact is particularly concerning for enterprise environments where these applications are widely deployed, as the vulnerability can be exploited through standard web-based attack vectors. Security teams must consider this vulnerability as part of their broader threat landscape, as it represents a pathway for persistent threats to establish footholds within networks through web-based delivery mechanisms.
Mitigation strategies for CVE-2013-5602 focus primarily on immediate version upgrades to patched releases of affected software. Mozilla released security updates for Firefox 25.0, Firefox ESR 17.0.10, and 24.1, as well as corresponding updates for Thunderbird and SeaMonkey to address the memory corruption issues. Organizations should prioritize immediate deployment of these patches across all affected systems to eliminate the vulnerability exposure. Additional mitigations include implementing web application firewalls to filter malicious content, disabling web workers in high-risk environments when possible, and employing content security policies to restrict proxy manipulation. Network monitoring should be enhanced to detect unusual memory access patterns or proxy-related anomalies that might indicate exploitation attempts. The vulnerability serves as a reminder of the importance of keeping web browser software up to date, as the memory corruption issues in web worker implementations require careful handling of proxy objects and memory management. Security administrators should also consider implementing browser hardening techniques and user education to reduce the attack surface, particularly in environments where users may encounter untrusted web content. Regular vulnerability assessments and penetration testing should include evaluation of web worker implementations and proxy handling code to identify similar memory corruption patterns that could represent future security risks.