CVE-2026-117969 in Firefox
Summary
by MITRE • 10/27/2026
Invalid pointer in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 159 and Firefox ESR 153.6.
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Analysis
by VulDB Data Team • 10/27/2026
The identified security flaw resides within the Just-In-Time compilation subsystem of the Mozilla SpiderMonkey JavaScript engine, specifically involving an invalid memory pointer dereference during the execution of optimized code paths. This type of vulnerability typically arises when the compiler generates machine code that assumes certain preconditions regarding object shapes or memory layouts which are not strictly enforced at runtime under all circumstances. When a crafted script triggers this specific condition, the JIT compiler may produce instructions that reference an invalid address in memory. Such errors represent a critical failure in the boundary checks and type safety mechanisms that are essential for maintaining isolation between different execution contexts within the browser environment.
From a technical perspective, this issue falls under the category of improper input validation leading to out-of-bounds access or use-after-free scenarios depending on the specific internal state at the time of exploitation. The Common Weakness Enumeration classifies such flaws generally as CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer or potentially CWE-416 Use After Free if the pointer references memory that has already been deallocated by the garbage collector but not yet zeroed out. In the context of modern browser architectures, these low-level memory corruption bugs are particularly dangerous because they bypass many of the higher-level security abstractions provided by the JavaScript language itself, exposing the underlying native code to malicious manipulation.
The operational impact of this vulnerability is severe due to its potential for remote code execution. An attacker could construct a specially designed web page containing malicious JavaScript that exploits this JIT compilation error. Upon loading and executing this script within an affected version of Firefox or Firefox ESR prior to patching, the browser process may crash immediately, resulting in a denial of service. More critically, if the memory corruption allows for arbitrary read or write operations, it could lead to remote code execution with the privileges of the user running the browser. This would enable attackers to install malware, steal sensitive data such as cookies and session tokens, or pivot further into internal networks depending on the victim's security posture.
To mitigate this risk, users must ensure that their browsers are updated to Firefox version 159 or later, including the Extended Support Release branch at version 153.6 or newer. These releases contain the necessary patches that correct the pointer validation logic within the JIT compiler and reinforce memory safety checks during code generation. Additionally, organizations should enforce automated update policies for all endpoints running these browsers to minimize exposure windows. Security teams can also monitor browser telemetry data for unusual spikes in crash reports associated with JavaScript engine failures as an indicator of potential exploitation attempts targeting unpatched systems.