CVE-2017-9781: Check Mk Project Check Mk

Medium severity, CVSS 6.1. EPSS: 1.6% chance of exploitation in the next 30 days.

A cross site scripting (XSS) vulnerability exists in Check_MK versions 1.4.0x prior to 1.4.0p6, allowing an unauthenticated remote attacker to inject arbitrary HTML or JavaScript via the _username parameter when attempting authentication to webapi.py, which is returned unencoded with content type text/html.

Affected products

• Check Mk Project Check Mk: version 1.4.0 only

Published 2017-06-21. Last modified 2026-06-17.