CVE-2026-109709 Information disclosure, privilege escalation in the Security: Process Sandboxing component
An attacker can exploit a flaw in the process sandboxing component to disclose information and escalate privileges in Firefox and Thunderbird.
- 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-2026-109709?
CVE-2026-109709 is a high-severity 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
Information disclosure, privilege escalation in the Security: Process Sandboxing component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
Weakness: CWE-200
Which versions are affected by CVE-2026-109709?
How do I fix CVE-2026-109709?
Upgrade to a fixed version.
Is CVE-2026-109709 being exploited?
There is no known exploitation of CVE-2026-109709 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-109709, GHSA-c4mq-cc7v-mw2m, UBUNTU-CVE-2026-109709.