PT-2026-34054 · Mailcow · Mailcow

Published 2026-04-21 · Updated 2026-04-21 · CVE-2026-40873

Positive Technologies (AI Summary)

CVSS v4.0

8.9

High

Base vector

AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:N

Name of the Vulnerable Software and Affected Versions mailcow: dockerized versions prior to 2026-03b

Description The Quarantine details modal injects attachment filenames into HTML without escaping, which allows arbitrary HTML and JavaScript execution. An attacker can send an email with a specially crafted attachment name; when an administrator views the quarantined item, the JavaScript executes in their browser, potentially leading to account takeover.

Recommendations Update to version 2026-03b.

Exploit

Fix

XSS

Weakness Enumeration

CWE-80

CWE-79

Related Identifiers

CVE-2026-40873

Affected Products

Mailcow

References · 3

• 🔥 https://github.com/mailcow/mailcow-dockerized/security/advisories/GHSA-2xjc-rg88-jvpp · Exploit
• https://nvd.nist.gov/vuln/detail/CVE-2026-40873 · Security Note
• https://twitter.com/VulmonFeeds/status/2046735729707856066 · Twitter Post