Vulnerability · Published Sep 1, 2026 · Assigned by mozilla
CVE-2026-84637Calendar invitation attachments could launch local executables
Critical 9.8
In plain English
A critical-severity unrestricted file upload in Thunderbird from Mozilla. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 50% of all known vulnerabilities).
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu:22.04:LTS | thunderbird | no fix listed | UBUNTU-CVE-2026-84637 |
| Ubuntu:24.04:LTS | thunderbird | no fix listed | UBUNTU-CVE-2026-84637 |
| Ubuntu:26.04:LTS | thunderbird | no fix listed | UBUNTU-CVE-2026-84637 |
| Ubuntu:26.10 | thunderbird | no fix listed | UBUNTU-CVE-2026-84637 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Thunderbird | see references |
Weakness: CWE-434 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H