Use-after-free in Mozilla products - CVE-2026-109729
Published: October 16, 2026
Vulnerability identifier: #VU155991
CSH Severity: High
CVSS v4: 8.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-109729
CWE-ID: CWE-416
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service and potentially execute arbitrary code.
The vulnerability exists due to use-after-free in the JavaScript Engine: JIT component when handling just-in-time compilation of JavaScript. A remote attacker can supply crafted JavaScript that triggers access to freed memory to crash the browser or potentially execute arbitrary code.
Affected software
Mozilla Firefox
Firefox ESR
Firefox for Android
Debian Linux
firefox-esr (Debian package)
Firefox ESR
Firefox for Android
Debian Linux
firefox-esr (Debian package)
How to mitigate CVE-2026-109729
Install security update from vendor's website.
Mozilla Firefox - update to 158.0
Firefox for Android - update to 158.0
Firefox ESR - addressed in versions 115.43.0, 153.5.0
firefox-esr (Debian package) - update to 153.5.0esr-1~deb13u1
Firefox for Android - update to 158.0
Firefox ESR - addressed in versions 115.43.0, 153.5.0
firefox-esr (Debian package) - update to 153.5.0esr-1~deb13u1