Description

Privilege escalation in the Address Bar component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, and Firefox ESR 140.17.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.8",
  "pubDate": "2026-09-29T13:17:47.300Z",
  "pubdate": "2026-09-29T13:17:47.300Z",
  "executiveSummary": "A privilege escalation vulnerability has been identified within the Address Bar component of the Mozilla Firefox browser. This security flaw allows a malicious actor to potentially bypass browser security boundaries by leveraging improper handling of URL or input processing mechanisms within the interface.\nThe vulnerability affects Firefox ESR 153.4, Firefox 157, and Firefox ESR 140.17. Successful exploitation could permit an attacker to execute operations with elevated privileges that exceed the standard constraints of the web content process, potentially leading to unauthorized access to browser-internal functions or sensitive user data.\nThe flaw stems from a lack of strict input validation or state management during address bar operations. An attacker would typically require a user to interact with a maliciously crafted URL or navigation sequence to trigger the escalation. Given the central role of the address bar in browser security and navigation, this vulnerability poses a significant risk to user integrity and privacy, necessitating immediate remediation via update deployment.",
  "technicalDetails": "The vulnerability resides within the Address Bar component, which is responsible for parsing user input, managing navigation states, and updating the browser chrome context. The root cause involves an insufficient validation of input parameters processed during navigation events, which fails to correctly maintain security boundaries between the web content process and the privileged browser chrome process.\nIn the Firefox multi-process architecture, the address bar operates within the privileged chrome context, whereas web content is isolated within sandboxed content processes. The escalation occurs when the browser incorrectly interprets malicious input within the address bar, causing the browser to execute privileged code or perform sensitive operations on behalf of an untrusted source. This breakdown in process separation allows an attacker to manipulate the browser into performing actions that it would otherwise restrict if the request originated from web content.\nThe attack flow typically follows these steps: 1) The attacker lures a user to a malicious page or provides a specially crafted link that, when processed by the Address Bar, triggers a navigation state mismatch. 2) The browser's input processing logic encounters an edge case where it fails to verify the origin or the legitimacy of the navigation request context. 3) By exploiting this logic flaw, the attacker forces the browser to transition into an inconsistent state, granting the malicious content elevated execution context. 4) With these escalated privileges, the attacker can execute JavaScript or internal browser functions that are normally restricted, such as accessing sensitive API endpoints, bypass SOP (Same-Origin Policy) protections, or performing unauthorized modifications to the browser configuration.\nAffected versions include Firefox ESR 153.4, Firefox 157, and Firefox ESR 140.17. The vulnerability does not require prior authentication from the attacker, though it generally requires social engineering to trick the user into triggering the navigation or interacting with the address bar in a specific, attacker-orchestrated manner. Post-exploitation, the attacker gains the ability to execute operations within the browser's chrome layer, which could result in full compromise of the user's browser-side session or system-level actions depending on the specific permissions available to the Firefox process."
}