CVE-2026-84128

Privilege escalation in the WebDriver BiDi component. This vulnerability was fixed in Firefox 155 and Thunderbird 155.

• Published Sep 1, 2026
• CVSS 8.8 high
• 0.4% chance of exploitation in the next 30 days (EPSS)
• A fix is available

CVE-2026-84128 at the National Vulnerability Database