Track vulnerabilities like this one.
Sign up free to get alerted when software you use is affected.
9.6
CVE-2026-109705: Firefox and Thunderbird may let malicious sites escape sandbox
CVE-2026-109705 · published 2 days ago
Summary
Older versions of Firefox, Firefox ESR, and Thunderbird can be tricked by a malicious website to break the browser's isolation and run code outside the intended safe area. This could allow an attacker to access data or perform actions on the user's system. Update the browsers to the latest versions to protect against this risk.
What to do
The CVE record does not list a fixed version. Check the vendor's site or the advisory links below - a fix may already be released.
Affected software
| Ecosystem | Vendor | Product | Affected versions |
|---|---|---|---|
| – | mozilla | firefox | All versions |
| Debian:12 | debian | firefox-esr | All versions |
| – | mozilla | thunderbird | All versions |
Original advisory text
DEBIAN-CVE-2026-109705
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.
References
- https://www.mozilla.org/security/advisories/mfsa2026-106/
- https://www.mozilla.org/security/advisories/mfsa2026-108/
- https://bugzilla.mozilla.org/show_bug.cgi?id=2040905
- https://security-tracker.debian.org/tracker/CVE-2026-109705 Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-109/
- https://www.mozilla.org/security/advisories/mfsa2026-110/
Severity
9.6
Critical
Type
CWE-416Use After Free
Timeline
Published13 Oct 2026
Updated15 Oct 2026
First seen13 Oct 2026
Track software like this
Free during beta