CVE-2026-40878
Lowmailcow-dockerized Login Page has Reflected Parameter Injection / Wrong-Context XSS Escaping
Published Apr 21, 2026 · Updated Aug 12, 2026 · Also known as GHSA-xv9r-j862-5hqf
Key Facts
Routine patching- CVE-2026-40878 is a low-severity vulnerability (CVSS 2.1 v4) affecting mailcow-dockerized.
- It is not listed in any known-exploited vulnerabilities catalog. No public exploit code is known.
- EPSS estimates a 1.0% probability of exploitation in the next 30 days.
- No fixed version is listed yet; check the vendor advisory for mitigations.
- Brandefense priority: routine patching, as no exploitation is known and its severity is moderate or low.
CVSS v4
2.1
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/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
EPSS (30-day exploit likelihood)
1.0%
Higher than 61.4% of all scored CVEs
Exploited in the wild
No known
Not in a known-exploited catalog
Public exploit code
None known
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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
1 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| mailcow-dockerized | >= < 2026-03b | n/a |
Timeline
Publicly disclosed
Apr 21, 2026
Last updated
Aug 12, 2026
Weakness Type
- CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
References
FAQ
Common Questions.
mailcow: dockerized is an open source groupware/email suite based on docker.
Affected: mailcow-dockerized versions >= < 2026-03b. The full list is in the CVE brief.
It is not listed in any known-exploited vulnerabilities catalog.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
No public exploit code is known.
No fixed version is listed yet; check the vendor advisory for mitigations.
Brandefense priority: routine patching, as no exploitation is known and its severity is moderate or low.
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