CVE-2026-40872: Mailcow Mailcow-Dockerized

Critical severity, CVSS 9.3. EPSS: 0.4% chance of exploitation in the next 30 days.

mailcow: dockerized is an open source groupware/email suite based on docker. In versions prior to 2026-03b, the admin dashboard's Autodiscover logs render the EMailAddress value (logged as the "user" field) without HTML escaping. By submitting an unauthenticated Autodiscover request with a crafted EMailAddress containing HTML/JS, the payload is stored in Redis and executed when an admin views the Autodiscover logs. Version 2026-03b fixes the vulnerability.

Affected products

• Mailcow Mailcow-Dockerized: before 2026-03b (fixed in 2026-03b)

Published 2026-04-21. Last modified 2026-06-17.