Sandbox Escape Vulnerability in Firefox by Mozilla
CVE-2026-100818

Currently unrated

Key Information:

Vendor: Mozilla
Status: Firefox
Vendor: CVE Published:; 29 September 2026

What is CVE-2026-100818?

The vulnerability stems from a use-after-free condition in the Widget: Gtk component, which allows attackers to escape the sandbox and potentially execute arbitrary code within affected Firefox versions. The flaw has been addressed in Firefox ESR 153.4, Firefox 157, and Firefox ESR 140.17. Users are encouraged to upgrade their browser to the latest version to safeguard against potential exploitation.

Affected Version(s)

Firefox 140.17

Firefox 153.4

Firefox 157

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2069399

https://www.mozilla.org/security/advisories/mfsa2026-100/

https://www.mozilla.org/security/advisories/mfsa2026-97/

Download the Critical Vulnerability Management Cheat Sheet

Timeline

Vulnerability published
Sep 29, 2026
Vulnerability Reserved
Sep 26, 2026

Credit

Mozilla

CVE-2026-100818 Data

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