CVE-2026-109764 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 vulnerability represents a critical failure within the Enterprise Policies subsystem of Mozilla Firefox, specifically allowing for the circumvention of security configurations that are intended to be immutable by end-users or standard administrators. This component is designed to enforce organizational rules and restrictions through policy files loaded at startup, which typically govern settings such as password managers, add-on installations, proxy configurations, and update behaviors. The flaw indicates a logic error in how these policies are parsed, validated, or applied during the browser initialization process, creating an avenue for attackers to bypass established security controls that were previously considered robust against user tampering.
From a technical perspective, this type of vulnerability often stems from insufficient validation of policy inputs or race conditions where configuration changes can be injected after initial policy loading but before enforcement mechanisms are fully locked down. By exploiting this flaw, an adversary could potentially disable critical protections such as the restriction on installing unsigned extensions, which is a common vector for malware distribution and persistent access in enterprise environments. The ability to bypass these policies undermines the principle of least privilege within managed devices, allowing malicious actors to operate with elevated capabilities that should have been restricted by organizational security baselines.
The operational impact of this vulnerability is significant for organizations relying on Firefox as their primary web browser under centralized management. If an attacker gains initial access to a user account or device, they can leverage this bypass to disable logging, prevent the installation of endpoint detection agents via browser extensions, or exfiltrate data through unrestricted proxy settings that might otherwise be blocked by corporate policy. This effectively neutralizes several layers of defense-in-depth strategies, making it easier for threat actors to maintain persistence and move laterally within a network without triggering alerts associated with policy violations.
This issue aligns closely with CWE-250, which describes execution with unnecessary privileges, as the vulnerability allows actions that exceed the intended scope of user permissions defined by enterprise policies. Furthermore, in the context of the MITRE ATT&CK framework, this flaw facilitates techniques related to Defense Evasion and potentially Command and Control, depending on how the bypassed settings are utilized. For instance, if proxy or network policy restrictions can be overridden, it may allow for data exfiltration channels that evade standard monitoring tools configured by security teams.
To mitigate this risk, organizations must ensure that all endpoints running Firefox are updated to version 158 for standard releases or version 153.5 for Extended Support Release (ESR) users immediately upon availability. Beyond patching, administrators should review their enterprise policy configurations to identify any dependencies on settings that might be susceptible to similar bypass techniques in the future. Implementing additional layers of security such as application whitelisting and strict network segmentation can provide compensating controls if immediate patching is not feasible for all systems. Regular auditing of browser configuration compliance against organizational standards is also recommended to detect any unauthorized modifications or policy deviations promptly.