CVE-2026-2787 in Firefox
Summary
by MITRE • 02/24/2026
Use-after-free in the DOM: Window and Location component. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.
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Analysis
by VulDB Data Team • 03/04/2026
This vulnerability represents a critical use-after-free condition within the Document Object Model implementation of Mozilla Firefox and Thunderbird browsers, specifically affecting the Window and Location components. The flaw occurs when the browser attempts to access memory that has already been freed, creating a potential exploitation vector for remote code execution. The vulnerability impacts multiple product versions including Firefox versions prior to 148, Firefox ESR versions prior to 115.33 and 140.8, and Thunderbird versions prior to 148 and 140.8, indicating a widespread exposure across the Mozilla ecosystem. Such vulnerabilities are classified under CWE-416 as use-after-free conditions, which are particularly dangerous because they can lead to memory corruption and arbitrary code execution.
The technical implementation of this vulnerability stems from improper memory management within the DOM's Window and Location objects, where the browser fails to properly track object lifecycles and reference counts. When a Window or Location object is destroyed, the memory allocated to it may be freed but references to that memory can persist in other parts of the browser's memory space. This creates a window where malicious web content can trigger the freeing of memory while simultaneously executing code that attempts to access the freed memory region. The flaw is particularly concerning because it operates at the core of web browser functionality where Window and Location objects are fundamental to page navigation, window management, and URL handling operations.
The operational impact of this vulnerability extends beyond simple browser instability to potential remote code execution capabilities. Attackers could craft malicious web pages that trigger the use-after-free condition, potentially leading to full system compromise when the browser executes arbitrary code within the context of the user's privileges. This vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as successful exploitation could enable attackers to execute malicious scripts or commands on affected systems. The widespread nature of the affected products means that a significant portion of users could be exposed to this risk, particularly those running older versions of Firefox ESR or Thunderbird that have not received the necessary security patches.
Mitigation strategies should prioritize immediate patching of all affected versions to prevent exploitation. Organizations should implement automated update mechanisms to ensure all browser installations remain current with security patches. Network administrators should consider implementing web filtering solutions that can block access to known malicious domains until patches are deployed. The vulnerability demonstrates the importance of proper memory management practices and highlights the need for comprehensive security testing of DOM implementations. Security teams should monitor for exploitation attempts through network traffic analysis and endpoint detection systems, as the use-after-free condition may manifest as unusual memory access patterns or browser crashes. Additionally, users should be educated about the risks of visiting untrusted websites and the importance of keeping their browsers updated to protect against such memory corruption vulnerabilities.