Vulnerability · Published Apr 21, 2026 · Assigned by GitHub_M
CVE-2026-40873mailcow: dockerized vulnerable to stored XSS in Quarantine attachment filenames
High 8.9
In plain English
A high-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 36% 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 Quarantine details modal injects attachment filenames into HTML without escaping, allowing arbitrary HTML/JS execution. An attacker can deliver an email with a crafted attachment name so that when an admin views the quarantine item, JavaScript executes in their browser, taking over their account. 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:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:N