CVE-2026-40878
mailcow-dockerized Login Page has Reflected Parameter Injection / Wrong-Context XSS Escaping
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.
INFO
Published Date :
April 21, 2026, 8:17 p.m.
Last Modified :
Oct. 26, 2026, 10:10 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 4.0 | LOW | [email protected] |
Solution
- Update mailcow to version 2026-03b or later.
- Ensure Twig auto-escaping is correctly configured.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-40878.
| URL | Resource |
|---|---|
| https://github.com/mailcow/mailcow-dockerized/security/advisories/GHSA-xv9r-j862-5hqf |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-40878 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-40878
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-40878 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-40878 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Translated by [email protected]
Oct. 26, 2026
Action Type Old Value New Value Added Translation Title: mailcow-dockerized de mailcow, Description: mailcow: dockerized es una suite de groupware/correo electrónico de código abierto basada en docker. En versiones anteriores a 2026-03b, la interfaz web de mailcow pasa la variable ’$_SERVER[’REQUEST_URI’]’ sin procesar a Twig como una variable de plantilla global y la renderiza dentro de un literal de cadena de JavaScript en el ayudante ’setLang()’ de ’base.twig’, confiando en el auto-escapado HTML predeterminado de Twig en lugar de la estrategia de escape ’js’ apropiada para el contexto. Además, el ayudante ’query_string()’ de Twig fusiona todos los parámetros ’$_GET’ actuales en los enlaces de cambio de idioma en la página de inicio de sesión, por lo que los parámetros proporcionados por el atacante se reflejan y se conservan a través de la navegación. La versión 2026-03b soluciona la vulnerabilidad. -
CVE Modified by [email protected]
Jun. 17, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'mailcow', 'product': 'mailcow-dockerized', 'versions': [{'status': 'affected', 'version': '< 2026-03b'}]}] -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 17, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-40878', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-04-22T13:39:14.669308Z'} -
New CVE Received by [email protected]
Apr. 21, 2026
Action Type Old Value New Value Added 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. Added CVSS V4.0 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 Added CWE CWE-79 Added Reference https://github.com/mailcow/mailcow-dockerized/security/advisories/GHSA-xv9r-j862-5hqf