CVE-2026-92038 in Firefox
Summary
by MITRE • 09/15/2026
Mitigation bypass in the Remote Settings Client component. This vulnerability was fixed in Firefox 156 and Firefox ESR 153.3.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 09/15/2026
The identified security issue represents a critical failure within the mitigation mechanisms of Mozilla's Remote Settings Client, a core infrastructure component responsible for distributing configuration updates to Firefox browsers across various platforms including desktop, Android, and iOS. This vulnerability allows an attacker or malicious actor to bypass established security controls designed to restrict how remote settings are applied, potentially leading to unauthorized modification of browser behavior without proper authentication or validation checks. The flaw undermines the integrity of the update mechanism by exploiting weaknesses in the logic that validates incoming configuration payloads against expected schemas or permission levels.
From a technical perspective, this vulnerability falls under the category of Improper Restriction of Operations within the Bounds of a Memory Buffer or Logic Error depending on the specific implementation details, but more accurately aligns with CWE-284: Improper Access Control and CWE-915: Improper Modification of Software Controls. The Remote Settings Client is designed to fetch JSON-based configuration files from Mozilla's servers which dictate features such as blocklists, safe browsing settings, and experimental feature flags. When the mitigation bypass occurs, it suggests that the client fails to adequately verify the source or integrity of specific directives within these payloads before applying them locally. This could allow a compromised server endpoint or a man-in-the-middle attacker injecting malicious configuration data to execute actions with higher privileges than intended by the default security posture.
The operational impact of this vulnerability is significant as it compromises the trust model between the browser client and its update infrastructure. If an adversary can bypass these mitigations, they could potentially disable critical security features such as phishing protection, enforce tracking prevention settings that expose user data to third parties, or inject malicious extensions silently without user consent. This erosion of control over the browsing environment directly impacts user privacy and system integrity. In enterprise environments relying on Firefox ESR for standardized deployment, this flaw could be exploited to push rogue configurations across entire fleets of devices if the update channel is compromised or if local policy enforcement mechanisms are circumvented through this specific client-side logic error.
This incident highlights the importance of rigorous validation in distributed configuration systems and aligns with MITRE ATT&CK technique T1059: Command and Scripting Interpreter where attackers might use script-like configurations to execute unintended actions, as well as T1482: Domain Fronting if used to mask malicious update sources. The vulnerability was addressed in Firefox version 156 and the Extended Support Release (ESR) version 153.3 by strengthening the validation logic within the Remote Settings Client codebase. These updates likely involve stricter schema enforcement, enhanced signature verification for configuration payloads, or additional checks on permission scopes before applying remote directives to ensure that only authorized changes are permitted.
To mitigate risks associated with similar vulnerabilities in distributed systems, organizations should ensure all Firefox instances are updated to the latest stable releases immediately upon availability of patches like those found in version 156 and ESR 153.3. Additionally, administrators deploying Firefox via Group Policy or configuration profiles should review their local override settings to ensure they do not inadvertently disable security features that rely on remote settings validation. Regular auditing of browser configurations and monitoring for unexpected changes in policy enforcement can help detect potential exploitation attempts early. Maintaining a robust patch management process is essential as vulnerabilities in core components like the Remote Settings Client pose systemic risks due to their widespread deployment across millions of endpoints globally.