Description

Privilege escalation in the DevTools component. This vulnerability was fixed in Firefox 156 and Firefox ESR 153.3.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.8",
  "pubDate": "2026-09-15T13:16:59.370Z",
  "pubdate": "2026-09-15T13:16:59.370Z",
  "executiveSummary": "A privilege escalation vulnerability has been identified within the DevTools component of Mozilla Firefox and Firefox ESR. In a standard browser environment, the DevTools component requires elevated operational privileges to facilitate deep debugging, DOM manipulation, and network inspection. A security flaw within this component allows an attacker to bypass standard security boundaries and escalate privileges from a restricted, low-privilege content process to a highly privileged system-level context.\nThis vulnerability compromises the browser's core isolation architecture, exposing affected installations to sandbox escapes and unauthorized system access. An attacker capable of exploiting this vulnerability can execute arbitrary commands and actions with the permissions of the browser process, effectively bypassing the Same-Origin Policy (SOP). This vulnerability affects versions of Firefox prior to 156 and Firefox ESR prior to 153.3. To mitigate the associated risks, organizations must deploy the updated versions immediately, as failure to do so leaves endpoints vulnerable to remote exploitation vectors that could lead to host compromise.",
  "technicalDetails": "The Mozilla Firefox DevTools component is constructed using web technologies but operates within a highly privileged execution environment compared to standard web content. It utilizes the Firefox DevTools Protocol to communicate between the debugging client and the debugging server actors. These actors run within a system context (the chrome privilege level) to inspect and control the behavior of the browser and active web pages. The browser security model relies on strict isolation between the low-privilege content process where untrusted web pages run and the high-privilege process where DevTools actors execute.\nThe root cause of this privilege escalation vulnerability lies in insufficient boundary validation or lack of strict origin sanitization when the DevTools component processes messages or API calls from unprivileged contexts. Normally, untrusted web content is restricted from invoking or interacting with the privileged methods of the DevTools actors. However, this flaw allows an attacker-controlled context to bridge the isolation barrier. By exploiting an unvalidated communication channel or a message-passing oversight, an attacker can manipulate the DevTools server into executing privileged operations on behalf of the unprivileged content.\nDuring an attack, a user is typically lured to a malicious webpage containing a script designed to target the browser's internal messaging subsystem. The exploit payload targets the exposed interfaces of the DevTools component. When the vulnerable receiver processes the malicious payload, it fails to verify the authorization or origin of the calling context. Consequently, the payload executes within the privileged DevTools scope, granting the exploit script access to XPCOM (Cross-Platform Object Model) interfaces and other critical system-level APIs that are restricted from standard web applications.\nOnce privilege escalation is successfully achieved, the attacker's capabilities match those of the local user running the browser process. Post-exploitation actions can include reading, writing, or deleting arbitrary files on the local filesystem, modifying critical browser security configurations, extracting sensitive session tokens, and installing unauthorized extensions. By leveraging XPCOM interfaces, the attacker can also escape the browser sandbox to execute arbitrary shell commands on the host operating system. The vulnerability is resolved in Firefox 156 and Firefox ESR 153.3 by enforcing rigorous origin validation and restricting access to privileged APIs."
}