CVE-2026-40872 CRITICAL

CVE-2026-40872: mailcow: dockerized vulnerable to stored XSS in autodiscover logs email address field

Vendor Mailcow
Product mailcow-dockerized
Weakness CWE-79 · XSS
Published April 21, 2026
Last update April 22, 2026
View on NVD All CVEs

CVSS base score

9.3/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction —
Confidentiality —
Integrity —

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

April 21, 2026 CVE published
April 22, 2026 Record updated