Vulnerability · Published Apr 21, 2026 · Assigned by GitHub_M
CVE-2026-40872mailcow: dockerized vulnerable to stored XSS in autodiscover logs email address field
Critical 9.3
In plain English
A critical-severity cross-site scripting in mailcow-dockerized from mailcow. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 30% of all known vulnerabilities).
Official description
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 (as reported)
| Vendor | Product | Versions |
|---|---|---|
| mailcow | mailcow-dockerized | < 2026-03b |
Weakness: CWE-79, CWE-80 · 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