CVE-2026-18223
Medium
Description
Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to validate the invited recipient's email address when redeeming team and guest invitation tokens, which allows an authenticated attacker to join a team or gain unauthorized access to private channels via a forwarded or leaked invitation link.. Mattermost Advisory ID: MMSA-2026-00747
SeverityMedium
CVSS5.0
Exploit probability—
Product
Mattermost Server
PublishedOct 16, 2026
First seenOct 16, 2026
Weakness typeCWE-863Incorrect authorization
How to fix
Update
- mattermost mattermost_server11.7.10, 11.8.6, 11.9.2 or later
Vendor advisories
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mattermost mattermost_server | 11.7.0 ≤ v < 11.7.10, 11.8.0 ≤ v < 11.8.6, 11.9.0 ≤ v < 11.9.2, 11.10.0 | 11.7.10, 11.8.6, 11.9.2 |
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