---
id: CVE-2026-9549
title: >-
  Stored cross-site scripting in the service discovery active check output in
  Checkmk <2.5.0p5, <2.4.0p31, <2.3.0p48, and all 2.2.0 versions allows an
  administrator who can configure active or custom checks to inject malicious
  HTML or Java…
summary: >-
  Stored cross-site scripting in the service discovery active check output in
  Checkmk <2.5.0p5, <2.4.0p31, <2.3.0p48, and all 2.2.0 versions allows an
  administrator who can configure active or custom checks to inject malicious
  HTML or Java…
severity: medium
cvss: 4.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N'
cwe:
  - CWE-79
vendor: checkmk
product: checkmk
affected:
  - checkmk = 2.2.0
  - checkmk = 2.3.0
  - checkmk = 2.4.0
  - checkmk = 2.5.0
published: '2026-06-08'
updated: '2026-10-06'
sourceUpdated: '2026-10-06T22:10:00.247'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-9549'
references:
  - url: 'https://checkmk.com/werk/17993'
    label: security@checkmk.com
tags:
  - nvd
epss: 0.00242
epssPercentile: 0.14044
ingestedAt: '2026-10-06T22:23:15.934Z'
---

## Overview

Stored cross-site scripting in the service discovery active check output in Checkmk <2.5.0p5, <2.4.0p31, <2.3.0p48, and all 2.2.0 versions allows an administrator who can configure active or custom checks to inject malicious HTML or JavaScript into check output that executes in the browser of an admin or a user with host read permissions when they run the check on the service discovery page.

## Affected

- `checkmk = 2.2.0`
- `checkmk = 2.3.0`
- `checkmk = 2.4.0`
- `checkmk = 2.5.0`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.