CVE-2026-40873CWE-79CWE-80

mailcow: dockerized vulnerable to stored XSS in Quarantine attachment filenames

High · published April 21, 2026

CVSS v4.0
8.9
EPSS
1%
Percentile
45.3
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v4.0
8.9 · HIGH
Vector
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
EPSS
0.00551 · 45.3th percentile
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)
Published
2026-04-21T19:15Z
EPSS history
Timeline
  • 21 APR 19:15Z
    mailcow: dockerized vulnerable to stored XSS in Quarantine attachment filenames
    cvelistv5