CVE-2026-109752 in Firefox
Summary
by MITRE • 10/13/2026
Use-after-free in the DOM: Workers component. This vulnerability was fixed in Firefox 158 and Firefox ESR 153.5.
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Analysis
by VulDB Data Team • 10/13/2026
The identified vulnerability represents a critical memory management error within the Document Object Model, specifically affecting the Workers component of Mozilla Firefox browsers. A use-after-free condition occurs when software continues to reference a pointer after it has been deallocated from system memory. In this specific context, the flaw resides in how the browser handles worker threads, which are background scripts that run independently of the main execution thread to perform complex tasks without blocking the user interface. When these workers interact with DOM elements or internal data structures, improper lifecycle management can lead to a scenario where an object is freed while still being referenced by another part of the application logic. This discrepancy creates a window of opportunity for malicious actors to exploit the dangling pointer before it is properly nullified or reallocated.
From a technical perspective, this flaw allows for arbitrary code execution under certain conditions. When memory that has been released is accessed, the program may read stale data or write to unintended locations in memory. If an attacker can control the content of the freed memory block through carefully crafted web pages or malicious scripts, they can manipulate the values stored at those addresses. This capability enables the overwriting of function pointers or object vtables, which are critical structures used for method dispatching in C++ based applications like Firefox. By redirecting execution flow to attacker-controlled shellcode, a remote code execution vulnerability is realized. The severity of this issue is compounded by its presence in widely deployed browser engines, making it a high-value target for drive-by download attacks and web-based exploit kits that seek to compromise end-user systems without direct interaction beyond visiting a malicious site.
The operational impact of this vulnerability extends beyond simple data corruption or application crashes. While unexploited instances might result in denial-of-service conditions due to segmentation faults, successful exploitation grants an attacker full control over the browser process context. This level of access can be leveraged to bypass security sandboxing mechanisms that are designed to isolate web content from the underlying operating system. Once inside this privileged context, attackers can install persistent malware, exfiltrate sensitive user data such as credentials and browsing history, or use the compromised machine as a pivot point for further network intrusions. The vulnerability affects both standard releases of Firefox version 158 and the Extended Support Release (ESR) branch at version 153.5, indicating that organizations relying on stable enterprise builds were also susceptible until patches were applied.
In terms of classification frameworks, this issue aligns with CWE-416, which defines use-after-free errors as a category of memory corruption vulnerabilities. It is frequently associated with the ATT&CK technique T1203, representing exploitation for client execution, where attackers leverage software flaws to run malicious code on target devices. The remediation strategy involves updating all instances of Firefox and Firefox ESR to their respective patched versions. For enterprise environments utilizing automated patch management systems, it is imperative to verify that the update policies are configured to pull these specific version updates promptly. Additionally, users should be advised to enable automatic security updates where possible to minimize the window of exposure. Security teams should also monitor for indicators of compromise related to browser-based exploit kits and ensure that endpoint detection and response solutions are tuned to detect suspicious memory access patterns or unusual process behaviors originating from web browsers.