CVE-2026-109737 in Firefox
Summary
by MITRE • 10/13/2026
Mitigation bypass in the Enterprise Policies component. This vulnerability was fixed in Firefox 158 and Firefox ESR 153.5.
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Analysis
by VulDB Data Team • 10/13/2026
The identified security issue represents a critical failure within the enterprise policy management subsystem of Mozilla Firefox, specifically affecting versions prior to 158 for standard releases and before 153.5 for Extended Support Release channels. Enterprise policies are designed to allow system administrators to enforce specific configurations across an organization's fleet of browsers, ensuring compliance with security standards and operational requirements. This vulnerability exploits a logic flaw that allows attackers or malicious actors to bypass these enforced restrictions, effectively nullifying the administrative controls intended to secure the browsing environment.
From a technical perspective, this constitutes a privilege escalation within the context of browser configuration enforcement. The flaw likely stems from an insufficient validation mechanism when processing policy directives, allowing specific inputs to circumvent checks that would normally block unauthorized actions or configurations. By bypassing these policies, an attacker can potentially disable security features such as content blocking, extension restrictions, or safe browsing protections that were explicitly mandated by the organization's IT department. This undermines the principle of least privilege and compromises the integrity of the managed endpoint.
The operational impact is significant for organizations relying on Firefox ESR for their workforce. If enterprise policies are bypassed, users may inadvertently access malicious websites, install unauthorized extensions that could lead to data exfiltration or keylogging, or disable telemetry controls essential for security monitoring. This creates a gap in the defense-in-depth strategy, as the browser no longer adheres to the baseline security posture defined by the administrator. The vulnerability essentially transforms a managed device into an unmanaged one from a policy enforcement standpoint, exposing it to threats that should have been mitigated at the application layer.
This type of flaw aligns with CWE-250, which describes execution with unnecessary privileges, and more specifically relates to CWE-863 regarding incorrect authorization checks within access control mechanisms. In terms of adversary behavior, this vulnerability facilitates techniques associated with MITRE ATT&CK T1074, data staged locally for exfiltration or evasion, as well as potential misuse of system tools if the policy bypass allows modification of security settings that protect against such activities. It also touches upon aspects of privilege escalation where a lower-privileged user gains capabilities reserved for higher-privileged administrative configurations without proper authentication or authorization validation.
To mitigate this risk, organizations must immediately update all Firefox installations to version 158 or later for standard releases and version 153.5 or later for ESR channels. Patching is the primary remediation strategy as it addresses the underlying code logic that permitted the bypass. Additionally, administrators should verify their policy deployment mechanisms to ensure that critical security policies are being applied correctly post-update. Regular auditing of browser configurations against expected enterprise standards can help detect any residual misconfigurations or attempts to exploit similar weaknesses in other components. Continuous monitoring for anomalous behavior related to extension installations or setting modifications remains essential to maintain a robust security posture despite the patching effort.