CVE-2026-92065 in Firefox
Summary
by MITRE • 09/15/2026
Sandbox escape due to incorrect boundary conditions in the Widget: Win32 component. This vulnerability was fixed in Firefox 156 and Firefox ESR 153.3.
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Analysis
by VulDB Data Team • 09/15/2026
The identified security flaw resides within the Widget: Win32 subsystem of Mozilla Firefox, specifically involving a failure in enforcing correct boundary conditions during memory or data structure operations. In complex software architectures like web browsers, sandboxing is a critical defense mechanism designed to isolate potentially untrusted content from sensitive system resources and privileged processes. When boundary checks are incorrectly implemented or bypassed due to logical errors, the integrity of this isolation layer is compromised. This particular vulnerability allows an attacker who can trick a user into visiting a specially crafted webpage to escape the browser's sandbox environment. The root cause typically involves off-by-one errors, integer overflows, or improper validation of array indices and buffer sizes within the Win32 widget implementation, which handles graphical user interface elements on Windows operating systems.
The operational impact of this vulnerability is severe because it elevates an attacker from a low-privilege context to one with broader system access capabilities. By escaping the sandbox, malicious code executed via the browser can interact directly with the underlying operating system without the restrictions imposed by the security container. This could lead to arbitrary code execution, allowing the attacker to install malware, exfiltrate sensitive data stored on the local machine, or pivot further into a network environment if the user is part of an enterprise infrastructure. The vulnerability affects both standard releases and extended support versions prior to their respective patches, highlighting the importance of timely updates across all deployment tiers.
From a classification perspective, this issue aligns with CWE-120 Buffer Copy without Checking Size of Input or CWE-787 Out-of-bounds Write depending on the specific memory corruption mechanism exploited within the boundary condition failure. In terms of offensive security frameworks such as MITRE ATT&CK, this vulnerability facilitates techniques related to Defense Evasion and Privilege Escalation, specifically allowing attackers to bypass application sandboxing mechanisms like Sandbox Escape (T1615). The exploitation vector is primarily remote via a web page, requiring user interaction or drive-by download scenarios where the malicious content triggers the flawed boundary check logic.
Mitigation strategies focus on immediate patch management and defensive configuration adjustments. Users must update their Firefox installations to version 156 for standard releases or version 153.3 for Extended Support Release (ESR) channels, as these versions contain the corrected code that properly validates input boundaries before processing widget-related operations. For enterprise environments relying on ESR, IT administrators should prioritize deploying this specific patch through their software distribution systems to ensure all endpoints are protected against sandbox escape attempts. Additionally, organizations can employ application whitelisting and strict content security policies to limit the execution of untrusted scripts within browser contexts, providing an additional layer of defense even if a vulnerability in the rendering engine or widget subsystem is exploited. Regular monitoring for anomalous process behavior originating from Firefox processes can also aid in detecting potential exploitation attempts in real-time.