CVE-2026-117946 in Firefox
Summary
by MITRE • 10/27/2026
Incorrect boundary conditions in the JavaScript Engine component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6.
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Analysis
by VulDB Data Team • 10/27/2026
The identified security issue resides within the core JavaScript engine implementation of Mozilla Firefox, specifically concerning incorrect boundary conditions during memory access operations. This type of vulnerability typically arises when the runtime environment fails to properly validate array indices or buffer offsets before performing read or write actions on allocated memory regions. In complex scripting environments like SpiderMonkey, which powers Firefox's JavaScript execution, such errors can lead to out-of-bounds reads or writes if input data is not rigorously checked against established limits. The flaw suggests that under specific circumstances involving crafted scripts, the engine may access memory locations outside the intended boundaries of a buffer, potentially allowing an attacker to read sensitive information from adjacent memory spaces or corrupt heap structures by writing invalid data.
From a technical perspective, this vulnerability aligns with CWE-125, which describes Out-of-bounds Read vulnerabilities, and potentially CWE-787, which covers Out-of-bounds Write scenarios depending on the exact nature of the boundary check failure. These weaknesses are critical because they undermine the fundamental memory safety guarantees expected in modern web browsers. When a browser processes maliciously crafted JavaScript code that triggers these incorrect boundary conditions, it can lead to undefined behavior within the execution context. This instability is not merely a crash risk but serves as a potential pathway for more severe exploitation vectors, including arbitrary code execution if an attacker can leverage memory corruption to hijack control flow or leak private data such as cookies, session tokens, or user credentials stored in browser memory.
The operational impact of this vulnerability extends beyond simple application instability. If exploited successfully, it could allow a remote attacker who hosts malicious web content to bypass security sandboxing mechanisms that rely on correct memory isolation between different tabs and processes. This compromise weakens the overall threat model for users browsing untrusted websites or visiting pages with embedded third-party scripts. The ability to perform out-of-bounds operations effectively breaks the assumption of safe execution, potentially leading to data exfiltration or full system compromise in worst-case scenarios where additional exploitation techniques are chained together.
To mitigate this risk, it is imperative that all users update their Firefox installations immediately to version 159 for standard releases and versions 115.44 and 153.6 for Extended Support Release channels. These updates contain the necessary patches that enforce stricter boundary checks within the JavaScript engine's memory management routines. Additionally, organizations should ensure that browser deployment policies are configured to automatically apply security updates promptly. Users can further reduce exposure by enabling enhanced tracking protection features which limit the ability of third-party scripts to execute complex operations in untrusted contexts. Regular maintenance and adherence to vendor-recommended update cycles remain the most effective defense against such memory safety vulnerabilities prevalent in dynamic scripting engines.