CVE-2026-92071 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 vulnerability represents a critical security flaw within the Mozilla Gecko rendering engine, specifically affecting the Widget subsystem for Windows operating systems. As a sandbox escape vector, this issue allows malicious content executed within the browser's restricted environment to break out into the host system with elevated privileges. The root cause lies in incorrect boundary condition handling during memory operations or input validation routines associated with Win32 widget interactions. In complex software architectures like Firefox, various components communicate through well-defined interfaces, but when these boundaries are not strictly enforced due to logical errors, an attacker can craft specific inputs that exceed expected limits. This overflow or out-of-bounds access enables the execution of arbitrary code outside the intended sandbox context, effectively neutralizing one of the primary defense mechanisms against web-based attacks.
From a technical perspective, this flaw falls under the category of improper input validation and boundary check failures. The vulnerability likely involves a scenario where user-controlled data is passed to Win32 API calls without adequate verification of array indices or buffer sizes. When the application fails to correctly calculate or enforce these limits, it permits writes to memory regions that should remain protected by the sandbox policy. This type of error is particularly dangerous because it bypasses process isolation techniques designed to contain potential exploits within a low-privilege context. The presence of such a flaw indicates a gap in the rigorous testing and static analysis processes typically employed for security-critical components like widget handling, where interaction with native operating system features requires strict adherence to safety constraints.
The operational impact of this vulnerability is severe, as it directly compromises the integrity and confidentiality of the user's system. An attacker who successfully exploits this sandbox escape could execute arbitrary code on the victim's machine with the same privileges as the browser process. Depending on how Firefox is configured and run, this often translates to full control over the local environment. This capability allows for the installation of malware, theft of sensitive data such as passwords and session cookies stored in plaintext or weakly encrypted formats, keylogging, and further lateral movement within a network if the user has broader access rights. The ability to escape the sandbox transforms what might otherwise be a contained cross-site scripting or remote code execution attempt into a direct system compromise, significantly increasing the risk profile for users browsing untrusted websites or visiting malicious pages designed specifically to trigger this condition.
This vulnerability is classified under Common Weakness Enumeration (CWE) categories such as CWE-120 Buffer Copy without Checking Size of Input and CWE-787 Out-of-bounds Write, depending on the specific mechanism used to achieve the escape. In terms of attack tactics, it aligns with MITRE ATT&CK techniques related to Defense Evasion and Privilege Escalation, specifically those involving sandbox evasion or container breakout strategies adapted for browser-based contexts. The exploitation chain typically involves crafting a malicious webpage that triggers the faulty boundary condition in the Win32 widget component, leading to memory corruption that is then leveraged to gain control over execution flow outside the sandboxed renderer process.
To mitigate this risk, it is imperative that all users update their Firefox installations immediately to version 156 or later for standard releases, and version 153.3 or later for Extended Support Release channels. These versions contain patches that correct the boundary condition logic within the affected component. Organizations should enforce automated patch management policies to ensure timely deployment of these updates across all endpoints. Additionally, users can reduce exposure by employing additional security layers such as strict content security policies in enterprise environments, utilizing browser extensions that restrict script execution on untrusted sites, and maintaining up-to-date antivirus solutions capable of detecting post-exploitation behaviors associated with sandbox escapes. Regular auditing of third-party add-ons is also recommended to minimize the attack surface presented to potential exploit attempts targeting known vulnerabilities in core components.