CVE-2017-11507: Check Mk Project Check Mk

Medium severity, CVSS 6.1. EPSS: 1% chance of exploitation in the next 30 days.

A cross site scripting (XSS) vulnerability exists in Check_MK versions 1.2.8x prior to 1.2.8p25 and 1.4.0x prior to 1.4.0p9, allowing an unauthenticated attacker to inject arbitrary HTML or JavaScript via the output_format parameter, and the username parameter of failed HTTP basic authentication attempts, which is returned unencoded in an internal server error page.

Affected products

• Check Mk Project Check Mk: version 1.2.8 only; version 1.4.0 only

Published 2017-12-11. Last modified 2026-06-17.