Vulnerability · Published Apr 21, 2026 · Assigned by GitHub_M
CVE-2026-40878mailcow-dockerized Login Page has Reflected Parameter Injection / Wrong-Context XSS Escaping
Low 2.1
In plain English
A low-severity cross-site scripting in mailcow-dockerized from mailcow. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.8% (higher than 57% of all known vulnerabilities). Ready-made attack tooling exists: Nuclei.
Official description
mailcow: dockerized is an open source groupware/email suite based on docker. In versions prior to 2026-03b, the mailcow web interface passes the raw `$_SERVER['REQUEST_URI']` to Twig as a global template variable and renders it inside a JavaScript string literal in the `setLang()` helper of `base.twig`, relying on Twig's default HTML auto-escaping instead of the context-appropriate `js` escaping strategy. In addition, the `query_string()` Twig helper merges all current `$_GET` parameters into the language-switching links on the login page, so attacker-supplied parameters are reflected and preserved across navigation. Version 2026-03b fixes the vulnerability.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| mailcow | mailcow-dockerized | < 2026-03b |
Weakness: CWE-79 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N