- Critical 9.6
CVE-2026-100818
Sandbox escape due to use-after-free in the Widget: Gtk component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, and Firefox ESR 140.17.
Scores
The facts
- Published
- 29 September 2026
- Last changed
- 5 October 2026
- NVD status
- Analyzed
- Severity
- Critical, CVSS 9.6 out of 10 (version 3.1)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H - Weakness
- Affects
- mozilla firefox
- mozilla thunderbird
- Known exploited
- Not in the CISA Known Exploited Vulnerabilities catalogue in this build.
- EPSS
- 0.3% chance of exploitation activity in the next 30 days (percentile 16).
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