CVE-2026-117889 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 of Mozilla Firefox, specifically involving incorrect boundary conditions during memory management or array indexing operations. In complex web applications that rely heavily on dynamic scripting, such as those utilizing large datasets or intensive computational loops, precise handling of data boundaries is critical to maintaining system integrity. When these boundaries are miscalculated, it can lead to out-of-bounds read or write vulnerabilities. These types of flaws allow the engine to access memory locations outside the intended allocation, which may contain sensitive information from other processes or overwrite adjacent memory structures that control program flow.
From a technical perspective, this vulnerability aligns with CWE-125, Out-of-bounds Read, and potentially CWE-787, Out-of-bounds Write, depending on whether the flaw results in data leakage or arbitrary code execution capabilities. The root cause typically stems from insufficient validation of array indices or buffer sizes before accessing memory addresses. In the context of browser engines, this is particularly dangerous because JavaScript operates within a sandboxed environment designed to prevent malicious scripts from affecting the host system. However, if an attacker can craft a specific script that triggers these boundary errors, they may bypass these security boundaries, leading to potential remote code execution or information disclosure.
The operational impact of such vulnerabilities extends beyond simple application crashes. While many instances result in denial-of-service conditions due to segmentation faults or engine termination, more sophisticated exploitation could allow an attacker to execute arbitrary commands on the victim's machine. This is especially relevant given that modern browsers are often used as gateways for enterprise applications and sensitive transactions. An adversary leveraging this flaw through a malicious website could potentially escalate privileges within the browser process, leading to further lateral movement or data exfiltration. The vulnerability was addressed in Firefox version 159, as well as extended support releases ESR 115.44 and ESR 153.6, ensuring that users of these versions are protected against this specific class of memory safety errors.
Mitigation strategies primarily involve maintaining up-to-date software installations to ensure the latest patches for the JavaScript engine are applied. For organizations deploying Firefox across their infrastructure, it is imperative to verify that all endpoints have received updates corresponding to version 159 or later, including the specified ESR branches. Additionally, implementing strict content security policies can help mitigate the impact of any remaining unpatched vulnerabilities by restricting the sources from which scripts are loaded and executed. Monitoring for unusual browser behavior or crashes in environments running older versions remains a critical operational practice until full patch compliance is achieved across all systems.