CVE-2026-40873

mailcow: dockerized vulnerable to stored XSS in Quarantine attachment filenames

State: Published
Severity: 8.9 High
Published: Apr 21, 2026
Updated: Apr 21, 2026
Reserved: Apr 15, 2026

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.

Scores

CVSS	Score	Vector	Source
4.0	8.9 High	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	GitHub_M

Weaknesses

CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-80 Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)

Affected Products

Product	Versions
mailcow-dockerizedmailcow	< 2026-03bAffected

References

https://github.com/mailcow/mailcow-dockerized/security/advisories/GHSA-2xjc-rg88-jvpp

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