CVE-2026-92061 in Firefox
Summary
by MITRE • 09/15/2026
Incorrect boundary conditions in the Security: Process Sandboxing component. This vulnerability was fixed in Firefox 156.
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Analysis
by VulDB Data Team • 09/15/2026
The identified security flaw resides within the process sandboxing mechanisms of Mozilla Firefox, specifically involving incorrect boundary condition handling during resource isolation operations. Process sandboxes are a critical defense-in-depth strategy employed by modern web browsers to limit the potential damage caused by malicious code execution. By restricting the permissions and access rights of renderer processes that handle untrusted content from websites, browsers ensure that even if an attacker successfully exploits a vulnerability in JavaScript or rendering engines, they cannot easily escape the sandbox to compromise the user's operating system or access sensitive local files. The specific issue described involves boundary conditions where the logic governing these restrictions fails to correctly validate input parameters or state transitions during certain edge cases. This misconfiguration can lead to scenarios where the sandbox enforcement is bypassed or weakened, allowing processes that should be strictly confined to perform actions outside their intended scope.
From a technical perspective, this vulnerability likely stems from an off-by-one error, improper array indexing, or flawed logic in the checks that determine whether specific system calls or file operations are permitted within the sandboxed environment. When boundary conditions are not rigorously enforced, it creates a gap between the theoretical security model and its practical implementation. For instance, if a process attempts to access a resource just outside an allowed range due to incorrect calculation of memory addresses or path limits, the operating system's mandatory access control mechanisms might be circumvented because the browser-level sandbox did not properly filter the request before it reached the kernel level. This type of flaw is particularly dangerous because it undermines one of the most effective layers of protection against drive-by download attacks and cross-site scripting exploits that escalate to remote code execution.
The operational impact of this vulnerability is severe, as it potentially allows an attacker who has achieved arbitrary code execution within a browser tab to escape the sandbox environment. Successful exploitation could lead to full system compromise, enabling the reading or modification of local files, installation of persistent malware, and access to sensitive user data such as saved passwords, cookies, and browsing history. This effectively negates the security benefits provided by the multi-process architecture that Firefox employs. Attackers can leverage this flaw in conjunction with other vulnerabilities to create a reliable exploit chain that transitions from web content execution to host-level control without triggering typical sandbox escape detections.
This issue aligns closely with CWE-20, which describes Improper Input Validation, as the root cause lies in the failure to properly validate inputs or boundary constraints within the security logic. Furthermore, it relates to ATT&CK technique T1610, specifically Sandbox Evasion, where attackers manipulate execution environments to avoid detection and restriction. The vulnerability highlights the complexity of maintaining robust isolation boundaries in complex software systems like web browsers, where numerous components interact dynamically under varying conditions.
To mitigate this risk, users must ensure that their Firefox installation is updated to version 156 or later, which includes the necessary patches to correct these boundary condition errors. Administrators should enforce automatic update policies across all endpoints to minimize exposure windows. Additionally, organizations can supplement browser-level protections with endpoint detection and response solutions that monitor for anomalous process behavior indicative of sandbox escapes, such as unexpected privilege escalation attempts or unauthorized file access patterns originating from browser processes. Regular security audits focusing on input validation logic in critical subsystems are also recommended to prevent similar boundary-related flaws in future software releases.