CVE-2026-109705 Sandbox escape, site isolation issue due to incorrect boundary conditions, use-after-free in the Networking component
A use-after-free in the Networking component allows sandbox escape and site isolation bypass, enabling code execution.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-109705?
CVE-2026-109705 is a critical use after free vulnerability in Mozilla Firefox, published on 13 Oct 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
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, Thunderbird 153.5, and Firefox ESR 115.44.
Weakness: CWE-416
Which versions are affected by CVE-2026-109705?
How do I fix CVE-2026-109705?
Upgrade to a fixed version.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-109705 being exploited?
There is no known exploitation of CVE-2026-109705 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-109705, GHSA-mjw9-3pg2-vh5w, UBUNTU-CVE-2026-109705.