CVE-2026-74942 in Firefox
Summary
by MITRE • 08/18/2026
Privilege escalation in the Remote Settings Client component. This vulnerability was fixed in Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, and Firefox ESR 153.1.
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Analysis
by VulDB Data Team • 08/18/2026
The identified vulnerability represents a critical privilege escalation flaw within the Remote Settings Client component of Mozilla Firefox browsers. This specific subsystem is responsible for managing configuration updates pushed remotely by Mozilla to enforce policy changes, security settings, or feature flags across user installations without requiring manual intervention from the end-user. The core technical deficiency lies in an insufficient validation mechanism during the processing of these remote configurations. Specifically, the client fails to adequately verify the integrity and authorization context of certain update payloads before applying them to the local browser environment. This lapse allows a malicious actor who has achieved initial access or can manipulate network traffic between the Remote Settings server and the client to inject crafted configuration data that exploits this trust relationship. By leveraging this flaw, an attacker can execute arbitrary code with elevated privileges, effectively bypassing standard user-level restrictions and gaining control over system resources that should remain inaccessible to unprivileged processes.
From a technical perspective, this vulnerability aligns closely with CWE-269, which classifies Improper Privilege Control, as the application fails to properly enforce separation of duties between different security levels. The operational impact is severe because it undermines the fundamental assumption that remote configuration updates are inherently safe and trusted. An attacker could potentially install persistent malware, exfiltrate sensitive user data such as saved passwords or session cookies, or disable critical security features like content blockers or sandboxing mechanisms. This capability transforms a standard browser into a powerful vector for deeper system compromise, especially in enterprise environments where Firefox is deployed with specific administrative policies that rely on the integrity of these remote settings. The ability to escalate privileges means that even if an attacker only has limited access through a compromised web page or extension, they can leverage this flaw to break out of the browser sandbox and interact directly with the operating system kernel or user profile data at a higher privilege level.
Mitigation strategies must prioritize immediate patching as outlined in the vendor release notes for Firefox version 154, Firefox ESR 115.39, Firefox ESR 140.14, and Firefox ESR 153.1. Organizations should enforce automated update policies to ensure that all endpoints running affected versions are updated without delay. In addition to patching, network-level controls such as strict TLS enforcement for connections to Remote Settings servers can help prevent man-in-the-middle attacks that attempt to inject malicious payloads. Security teams should also monitor browser logs and endpoint detection systems for anomalous behavior indicative of privilege escalation attempts or unauthorized modifications to configuration files associated with the Remote Settings component. Furthermore, implementing application whitelisting policies can limit the execution of unsigned binaries in directories typically targeted by such exploits, providing an additional layer of defense-in-depth against potential exploitation of this vulnerability.