CVE-2026-118007 in Firefox
Summary
by MITRE • 10/27/2026
Use-after-free in the JavaScript: GC component. This vulnerability was fixed in Firefox 159.
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Analysis
by VulDB Data Team • 10/27/2026
The identified vulnerability represents a critical memory management error within Mozilla Firefox, specifically located in the Garbage Collection subsystem of its JavaScript engine. As a use-after-free flaw, this defect arises when the application continues to reference a block of memory that has already been deallocated and potentially reused for other purposes. In the context of modern web browsers, where complex scripts are executed dynamically, such errors can lead to severe security implications if an attacker can manipulate the timing or state of garbage collection processes. The vulnerability was addressed in Firefox version 159, marking a significant step toward hardening the browser against memory corruption attacks that have historically been among the most dangerous classes of vulnerabilities due to their potential for arbitrary code execution.
From a technical perspective, use-after-free vulnerabilities occur when pointers are not properly invalidated after the associated object is destroyed or freed from memory. In JavaScript engines like SpiderMonkey, which powers Firefox, objects are managed through automatic garbage collection cycles that identify and reclaim unused memory. If an internal state variable retains a reference to an object that has been collected, any subsequent access to that pointer will read from invalid memory locations. This can result in unpredictable behavior ranging from application crashes to the corruption of adjacent data structures. When exploited by malicious actors, these conditions allow for precise control over program flow and memory contents, facilitating remote code execution on the victim's system under the context of the browser process.
The operational impact of this vulnerability is severe because it affects a core component responsible for managing script execution resources. Attackers could potentially craft specific web pages or scripts that trigger the premature deallocation of JavaScript objects while maintaining active references to them within other parts of the engine. By carefully controlling memory allocation patterns, an attacker might overwrite freed memory with controlled data, thereby gaining the ability to execute arbitrary commands on the target machine. This poses a direct threat to user privacy and system integrity, as successful exploitation could lead to full compromise of the host environment without requiring additional privileges or social engineering beyond visiting a malicious website.
Industry standards classify this type of flaw under CWE-416, which defines use-after-free conditions where references are used after they have been invalidated. This categorization highlights the fundamental failure in memory safety protocols within the software lifecycle. Furthermore, from an offensive security perspective aligned with MITRE ATT&CK frameworks, such vulnerabilities often facilitate initial access and privilege escalation techniques by allowing attackers to bypass standard sandboxing mechanisms inherent in browser architectures. The exploitation of these flaws is a common vector for drive-by download attacks and zero-day exploits targeting widespread desktop applications like Firefox.
Mitigation strategies primarily involve the timely application of vendor-provided patches, as demonstrated by the release of Firefox 159 which contains the fix for this specific issue. Organizations should ensure that their deployment pipelines automatically update browsers to incorporate these security fixes promptly. Additionally, developers and administrators can employ defense-in-depth measures such as enabling memory protection features like ASLR (Address Space Layout Randomization) and DEP (Data Execution Prevention), although these are mitigations rather than solutions to the underlying code defect. For end-users, maintaining up-to-date software versions remains the most effective countermeasure against exploitation of known vulnerabilities in browser components.