Description

Sandbox escape due to incorrect boundary conditions in the XPCOM component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.6",
  "pubDate": "2026-09-29T13:17:47.193Z",
  "pubdate": "2026-09-29T13:17:47.193Z",
  "executiveSummary": "This vulnerability involves a sandbox escape condition residing within the Cross-Platform Component Object Model (XPCOM) framework of the Firefox browser.\nThe flaw stems from incorrect boundary condition handling, which permits an attacker to circumvent the security sandbox, granting unauthorized access to the host operating system or escalated privileges within the browser environment.\nThe vulnerability affects multiple release channels, specifically Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.\nExploitation of this flaw allows an attacker to break out of the restricted content process, posing a critical risk to user data confidentiality and system integrity.\nThe attack typically requires the execution of arbitrary code within the sandboxed environment, often delivered via malicious web content or a previously chained exploit in the browser engine.\nSuccessful exploitation grants the attacker the ability to perform operations outside the browser's security boundaries, effectively neutralizing the isolation provided by the sandbox architecture.",
  "technicalDetails": "The root cause of this vulnerability is an improper validation of boundary conditions within the XPCOM component architecture.\nXPCOM is a critical framework for Firefox that facilitates cross-platform component management and communication between different browser modules. When internal components interface with one another, especially across privilege boundaries, specific memory or data structures must be constrained to prevent invalid access.\nIn this instance, the vulnerability arises when the XPCOM component processes input or state transitions where the boundary conditions are inadequately verified. This failure allows for an out-of-bounds access scenario or logical inconsistency, which can be leveraged to trigger a sandbox escape.\nThe attack flow typically begins with the exploitation of a preliminary vulnerability in the browser's rendering engine or JavaScript engine, allowing the attacker to execute arbitrary code within the low-privilege content process. Once code execution is achieved, the attacker directs the process to interact with the vulnerable XPCOM component.\nBy providing specially crafted inputs or triggering specific sequences of method calls that violate the assumed architectural constraints of the XPCOM object, the attacker exploits the boundary condition flaw. This manipulation corrupts the control flow or data state of the privileged browser process, effectively bypassing the sandbox's mandatory access control checks.\nOnce the sandbox boundary is traversed, the attacker can execute code with the elevated privileges of the browser's main process. This enables unauthorized actions, such as file system access, credential exfiltration, or the installation of persistent malicious code on the underlying host system.\nAffected versions include Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17. The exploit does not inherently require authentication but depends on the attacker's ability to first achieve code execution within the browser's restricted process. The network exposure is limited to the initial vector, usually requiring the user to navigate to a malicious URL or interact with compromised content."
}