CVE-2026-109714 in Firefox
Summary
by MITRE • 10/13/2026
Incorrect boundary conditions in the Layout component. This vulnerability was fixed in Firefox 158.
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Analysis
by VulDB Data Team • 10/13/2026
The identified vulnerability resides within the Layout component of Mozilla Firefox and stems from incorrect handling of boundary conditions during rendering operations. In web browsers, layout engines are responsible for calculating the position and size of elements on a webpage based on CSS rules and HTML structure. When these calculations involve edge cases or specific combinations of styles that push values to their limits, improper validation can lead to memory corruption issues. Specifically, this flaw likely involves an out-of-bounds read or write scenario where the application fails to correctly verify array indices or buffer lengths before accessing data structures associated with layout objects. Such errors are particularly dangerous because they occur during the processing of complex web content, allowing a remote attacker to craft a malicious webpage that triggers these faulty boundary checks when rendered by the victim's browser.
From a technical perspective, this type of vulnerability is often categorized under CWE-125, which describes Out-of-bounds Read, or potentially CWE-787, an Out-of-bounds Write, depending on whether the exploit results in information disclosure or arbitrary code execution. The root cause lies in the lack of rigorous bounds checking within the C++ codebase that powers Firefox's Gecko engine. When a webpage contains specially crafted CSS properties or DOM structures that exceed expected limits, the layout algorithm may access memory locations outside the allocated buffer. This can lead to reading sensitive data from adjacent memory regions or overwriting critical control data such as function pointers and return addresses. The severity of this issue is amplified by its potential for remote code execution, a capability highly sought after in modern cyber attacks targeting browser-based entry points.
The operational impact of this vulnerability allows an attacker who hosts a malicious website to potentially execute arbitrary code with the privileges of the user running Firefox. By leveraging techniques aligned with MITRE ATT&CK tactic T1203, specifically Exploitation for Client Execution, an adversary can deliver payloads that bypass standard security controls if other mitigations like ASLR or DEP are not fully effective against this specific memory corruption pattern. Successful exploitation could lead to a complete compromise of the user's system, including theft of credentials, installation of malware, and lateral movement within networked environments. Since Firefox is widely used across various operating systems, the blast radius extends beyond individual users to potentially affect enterprise deployments where browser security is critical for maintaining organizational integrity.
Mitigation strategies primarily involve applying the software update that addresses this flaw in Firefox version 158 or later. Users should ensure their browsers are configured to auto-update to receive these patches promptly. For organizations managing fleets of devices, deploying updates through centralized management tools such as Mozilla Enterprise policies is recommended to enforce compliance and reduce exposure windows. Additionally, users can employ browser hardening techniques like NoScript or uMatrix to restrict the execution of untrusted JavaScript on suspicious sites, thereby reducing the attack surface even before patches are applied. Security teams should also monitor for indicators of compromise related to memory corruption exploits in browsers and ensure that endpoint detection and response solutions are tuned to detect anomalous behavior associated with such attacks.