Critical 9.8Published Sep 1, 2026

CVE-2026-84637Calendar invitation attachments could launch local executables

Updated under an hour ago (2026-10-19 09:10 UTC)

Does this affect you?

It affects Mozilla Thunderbird. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

Do this next

Start free and add your stack

Free account, 1 product

Every CVE for Mozilla Thunderbird

Exploited in the last 30 days

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.

CVSS: 9.8 CRITICAL (v3.1, CISA ADP)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE): CWE-434
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: mozilla
NVD analysis: Analyzed
Record last updated: Sep 2, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Mozilla Thunderbird mozilla:thunderbird (from the name)	153.2 builds before 153.* not affected; from 154 not affected	CNA record
mozilla thunderbird mozilla:thunderbird	before 153.2.0; from 154.0 before 155.0	NVD

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2043878permissions-required
https://www.mozilla.org/security/advisories/mfsa2026-78/vendor-advisory
https://www.mozilla.org/security/advisories/mfsa2026-88/vendor-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.