CVE-2026-109740

CriticalCVSS 9.6

Published: 13/10/2026(UTC)Updated: 19/10/2026(UTC)Translated: 14/10/2026(UTC)NVD NIST

Exploitation Probability (EPSS)

Low risk

0.16%

5th percentile - higher than 5% of all known CVEs

Summary

Sandbox escape due to incorrect boundary conditions in the Widget: Win32 component. The flaw was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.

Risk Assessment

Sandbox escape could allow an attacker to execute code outside browser restrictions, increasing the risk of system compromise or data theft.

Recommendation

Immediately update Firefox or Thunderbird to the patched version.

Other vulnerabilities in Firefox

See all

CVE-2026-109755Critical
A vulnerability in the DOM: Content Processes component allows sandbox escape. It was fixed in Firefox 158 and Thunderbird 158.
CVE-2026-109745Critical
Sandbox escape due to uninitialized memory in the DOM: Web Serial component. It was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
CVE-2026-109708Critical
Sandbox escape due to incorrect boundary conditions in the Networking component. The vulnerability was fixed in Firefox 158, Firefox ESR 153.5, and Thunderbird 158 and 153.5.
CVE-2026-109707Critical
Sandbox escape due to use-after-free in the Networking component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
CVE-2026-109705Critical
Sandbox escape, site isolation issue due to incorrect boundary conditions, use-after-free in the Networking component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
CVE-2026-106016Critical
Mitigation bypass in the File Handling component. This vulnerability was fixed in Firefox 157.0.1 and Thunderbird 158.
CVE-2026-100829Critical
Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157.
CVE-2026-100828Critical
Mitigation bypass in the Bookmarks & History component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157.
CVE-2026-100819Critical
Sandbox escape due to incorrect boundary conditions in the XPCOM component. Fixed in multiple Firefox and Thunderbird versions.
CVE-2026-100818Critical
Sandbox escape due to use-after-free in the Widget: Gtk component. Fixed in multiple Firefox and Thunderbird versions.

Original NVD description (English source)

Sandbox escape due to incorrect boundary conditions in the Widget: Win32 component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS