Description

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.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.8",
  "pubDate": "2026-08-18T13:17:30.673Z",
  "pubdate": "2026-08-18T13:17:30.673Z",
  "executiveSummary": "A privilege escalation vulnerability has been identified within the Remote Settings Client component of the Mozilla Firefox ecosystem. This security flaw allows an authenticated attacker to elevate their execution privileges within the context of the affected application by exploiting weaknesses in how remote configuration and settings payloads are processed. The vulnerability directly impacts multiple editions of the browser, specifically Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, and Firefox ESR 153.1.\nSuccessful exploitation of this flaw can lead to unauthorized elevation of privilege, potentially granting an adversary broader access to system resources, sensitive data stores, or execution contexts normally restricted by the browser sandbox architecture. The risk implications are severe, as an attacker who has already achieved code execution or manipulation capabilities within a lower privilege tier can leverage this flaw to subvert security boundaries.\nWhile specific prerequisites regarding local access or prior compromise of execution vectors depend on the operational environment, the flaw fundamentally stems from improper validation or handling of client-side remote updates. Mitigating this issue requires immediate application of the official vendor patches provided in the referenced product versions.",
  "technicalDetails": "The vulnerability resides in the Remote Settings Client component, a subsystem responsible for dynamically fetching, parsing, and applying remote configuration data, blocklists, and feature flags within the browser architecture. The root cause involves inadequate validation, improper boundary checking, or insecure deserialization/processing of data payloads received from the remote settings infrastructure.\nIn a typical attack flow, an adversary interacts with or spoofs the Remote Settings Client data pipeline to supply a maliciously crafted configuration payload. Because the Remote Settings Client operates with elevated operational privileges or trusts incoming synchronization data without rigorous cryptographic or structural verification, the malicious payload is processed by the underlying engine.\nDuring execution, the vulnerable component misinterprets the data structures or instructions contained within the payload, leading to memory corruption, improper object instantiation, or logic flaws that bypass security checks. This enables the attacker to transition from a restricted execution context to a higher privilege level associated with the browser component.\nThe attack vector typically requires the capability to influence or intercept the communication channel of the Remote Settings Client, or leverage an existing low-privilege foothold within the application to inject malicious updates into the local cache or synchronization loop. Authentication and privilege requirements vary based on whether the vector relies on local file manipulation or network-based man-in-the-middle mechanisms against the update protocol.\nPost-exploitation impact includes the potential execution of arbitrary code with the privileges of the affected component, bypassing security controls, and facilitating persistent system compromise or further lateral movement within the host operating system. The vulnerability is fully resolved in Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, and Firefox ESR 153.1 through enhanced validation and secure handling protocols within the Remote Settings Client component."
}