- Critical 9.6
CVE-2026-109707
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.
Scores
The facts
- Published
- 13 October 2026
- Last changed
- 13 October 2026
- NVD status
- Deferred
- 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
- 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 22).
Is there a Securelyn advisory?
Not yet. Securelyn writes plain-English advisories for the flaws that matter most to businesses. Subscribe to the digest to hear about them.