Main Vulnerability Database Vulnerabilities #VU146627

Input validation error in Mozilla Firefox and Firefox for Android - CVE-2026-84126

Published: September 1, 2026

Vulnerability identifier: #VU146627

CSH Severity: High

CVSS v4: 8.4 [CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-84126

CWE-ID: CWE-20

Exploitation vector: Remote access

Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to execute arbitrary code.

The vulnerability exists due to improper input validation in the Layout: Grid component when rendering crafted web content. A remote attacker can supply content that triggers incorrect boundary conditions to execute arbitrary code.

Affected software

Mozilla Firefox
Firefox for Android

How to mitigate CVE-2026-84126

Install security update from vendor's website.

Mozilla Firefox - update to 155.0
Firefox for Android - update to 155.0

External References

Related Security Bulletins