CVE-2026-109740

A flaw was found in Firefox. Incorrect boundary condition handling in the Win32 widget component allows an attacker to escape the browser's restricted sandbox environment. An attacker who has compromised a sandboxed content process could exploit this vulnerability to achieve privilege escalation and execute arbitrary code on the underlying operating system.

This vulnerability is rated as Important severity because escaping the client sandbox allows an attacker who has compromised a content process to execute arbitrary code with the privileges of the host process. However, the vulnerable boundary condition resides exclusively within the Win32 widget subsystem developed for Microsoft Windows. Red Hat Enterprise Linux builds of Firefox and Thunderbird utilize the GTK windowing implementation and do not include the Windows-specific code, preventing exposure in Red Hat environments.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.