Improper access control in Mozilla products - CVE-2026-109759
Published: October 16, 2026
Vulnerability identifier: #VU156036
CSH Severity: Medium
CVSS v4: 5.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-109759
CWE-ID: CWE-284
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to bypass site isolation and potentially access resources across site boundaries.
The vulnerability exists due to inadequate enforcement of site-isolation boundaries in the Networking component when handling network operations. A remote attacker can trigger affected network processing to cross boundaries intended to separate different sites.
Affected software
Firefox ESR
Mozilla Firefox
Firefox for Android
Debian Linux
firefox-esr (Debian package)
Mozilla Firefox
Firefox for Android
Debian Linux
firefox-esr (Debian package)
How to mitigate CVE-2026-109759
Install security update from vendor's website.
Firefox ESR - update to 153.5.0
Firefox for Android - update to 158.0
Mozilla Firefox - update to 158.0
firefox-esr (Debian package) - update to 153.5.0esr-1~deb13u1
Firefox for Android - update to 158.0
Mozilla Firefox - update to 158.0
firefox-esr (Debian package) - update to 153.5.0esr-1~deb13u1