CVE-2026-84637
Critical
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.
SeverityCritical
CVSS9.8
Exploit probability—
Product
Mozilla Thunderbird
PublishedSep 1, 2026
First seenSep 1, 2026
Weakness typeCWE-434Unrestricted upload of dangerous file type
How to fix
Update
- mozilla thunderbird153.2.0, 155.0 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mozilla thunderbird | v < 153.2.0, 154.0 ≤ v < 155.0 | 153.2.0, 155.0 |
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