CVE-2009-3371 in Firefox
Summary
by MITRE
Use-after-free vulnerability in Mozilla Firefox 3.5.x before 3.5.4 allows remote attackers to cause a denial of service (application crash) or possibly execute arbitrary code by creating JavaScript web-workers recursively.
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Analysis
by VulDB Data Team • 08/24/2021
The vulnerability identified as CVE-2009-3371 represents a critical use-after-free flaw in Mozilla Firefox versions 3.5.x prior to 3.5.4 that enables remote attackers to potentially execute arbitrary code or cause denial of service through recursive JavaScript web-worker creation. This vulnerability operates within the browser's JavaScript execution environment and specifically targets the memory management mechanisms used for handling web workers. The issue stems from improper handling of memory allocation and deallocation when multiple web workers are created recursively, leading to situations where freed memory locations are accessed after being reallocated for other purposes. The flaw manifests when the browser's JavaScript engine processes recursive web-worker creation patterns that ultimately result in memory corruption. This type of vulnerability falls under the CWE-416 category of Use After Free, which is a well-documented weakness in software security that occurs when a program continues to reference memory after it has been freed, creating potential for arbitrary code execution or system instability. The vulnerability is particularly dangerous because it can be exploited through web-based attacks without requiring any local privileges or user interaction beyond visiting a malicious website. When exploited, the vulnerability allows attackers to manipulate the memory layout of the Firefox process, potentially leading to code execution in the context of the browser application.
The technical exploitation of this vulnerability requires attackers to craft malicious JavaScript code that creates web workers recursively, causing the browser's memory management system to encounter a use-after-free condition during garbage collection cycles. The recursive nature of the web-worker creation ensures that memory is allocated and deallocated in a specific pattern that triggers the vulnerability. This pattern typically involves creating a web worker that in turn creates another web worker, and so on, until the memory management system encounters a freed memory location that is subsequently accessed. The attack vector operates entirely through web content, making it particularly dangerous for web browsers that execute untrusted code from remote sources. The vulnerability demonstrates how modern browser security models can be compromised through seemingly benign JavaScript operations that exploit underlying memory management flaws. The exploitation process involves careful crafting of JavaScript code that can be executed in the browser's context, leveraging the browser's web worker API to trigger the specific memory corruption scenario that leads to the use-after-free condition.
The operational impact of CVE-2009-3371 extends beyond simple denial of service to potentially enable full remote code execution on vulnerable systems. When successfully exploited, the vulnerability allows attackers to execute arbitrary code with the privileges of the Firefox process, which typically runs with the same privileges as the user who launched the browser. This could lead to complete system compromise if the user has elevated privileges, or provide attackers with a foothold for further attacks within the network. The vulnerability affects all Firefox 3.5.x versions before 3.5.4, making it a significant concern for organizations that had not yet updated their browser installations. The remote nature of the attack means that users do not need to perform any specific actions beyond visiting a malicious website, making it particularly dangerous in phishing campaigns or drive-by download scenarios. Organizations running older versions of Firefox were exposed to this vulnerability for an extended period, as it was not immediately patched and required users to update their browser installations to mitigate the risk.
Mitigation strategies for CVE-2009-3371 focus primarily on updating to patched versions of Firefox, specifically Firefox 3.5.4 or later, which contain the necessary memory management fixes to prevent the use-after-free condition. System administrators should implement comprehensive patch management policies to ensure all browser installations are kept current with security updates. Additional protective measures include implementing content filtering solutions that can detect and block malicious JavaScript patterns, enabling sandboxing features within the browser, and configuring browser security settings to limit web worker functionality where possible. The vulnerability highlights the importance of proper memory management in browser security and the need for regular security updates to address newly discovered flaws. Organizations should also consider implementing network-based intrusion detection systems that can identify attempts to exploit this vulnerability through malicious web content. The remediation process requires careful testing of updates to ensure compatibility with existing web applications while maintaining security posture. Security teams should monitor for indicators of compromise related to this vulnerability and maintain awareness of similar memory corruption vulnerabilities that may affect other browser implementations. The vulnerability serves as a reminder of the critical importance of keeping browser software updated and the potential consequences of running outdated security software in enterprise environments.