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CRITICAL

CVE-2026-84637

CVSS v3

9.8

CRITICAL

EPSS Score

0.6 %

exploit probability, as of 2026-09-28

CISA KEV

No

known exploited

Exploitation

—

SSVC status

Description

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.

Technical details

Published
2026-09-01
Last Modified
2026-09-02

Frequently asked questions

What is CVE-2026-84637?

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.

Is CVE-2026-84637 actively exploited?

Active exploitation of CVE-2026-84637 has not been confirmed. Its EPSS score was 0.6% on 2026-09-28, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-84637?

CVE-2026-84637 has a CVSS v3 base score of 9.8 (CRITICAL severity).

Is CVE-2026-84637 affecting your environment?

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