CVE-2026-84138

Denial-of-service in the PDF Viewer component. This vulnerability was fixed in Firefox 155 and Thunderbird 155.

• Published Sep 1, 2026
• CVSS 6.5 medium
• 0.4% chance of exploitation in the next 30 days (EPSS)
• A fix is available

CVE-2026-84138 at the National Vulnerability Database