CVE-2026-84637: thunderbird: Thunderbird: Arbitrary code execution via malicious calendar invitation attachments

Severity: Critical

CVSS Score: 9.8

Malicious calendar invitations could use file URI attachments to launch local or network-hosted executables on Windows, bypassing Thunderbird's normal executable attachment protections. With the new invitation display enabled, the attachment could also appear under a misleading filename. This vulnerability was fixed in Thunderbird 154 and Thunderbird 153.2.