PT-2026-34057 · Mailcow · Mailcow-Dockerized

Published 2026-04-21 · Updated 2026-04-21 · CVE-2026-40878

NVD

CVSS v4.0

2.1

Low

Base vector

AV:N/AC:L/AT:P/PR:N/UI:A/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

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.

Fix

XSS

Weakness Enumeration

CWE-79

Related Identifiers

CVE-2026-40878

Affected Products

Mailcow-Dockerized

References · 2

• https://nvd.nist.gov/vuln/detail/CVE-2026-40878 · Security Note
• https://github.com/mailcow/mailcow-dockerized/security/advisories/GHSA-xv9r-j862-5hqf · Note