---
id: CVE-2026-8833
title: >-
  Improper neutralization of HTML-encoded characters in the URL validation
  function in Checkmk <2.5.0p5, <2.4.0p31, <2.3.0p48, and all 2.2.0 versions
  allows an authenticated user to bypass URL validation and inject malicious
  URLs such as j…
summary: >-
  Improper neutralization of HTML-encoded characters in the URL validation
  function in Checkmk <2.5.0p5, <2.4.0p31, <2.3.0p48, and all 2.2.0 versions
  allows an authenticated user to bypass URL validation and inject malicious
  URLs such as j…
severity: medium
cvss: 5.4
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/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-2026-8833'
references:
  - url: 'https://checkmk.com/werk/20002'
    label: security@checkmk.com
tags:
  - nvd
epss: 0.00238
epssPercentile: 0.13584
ingestedAt: '2026-10-06T22:23:15.934Z'
---

## Overview

Improper neutralization of HTML-encoded characters in the URL validation function in Checkmk <2.5.0p5, <2.4.0p31, <2.3.0p48, and all 2.2.0 versions allows an authenticated user to bypass URL validation and inject malicious URLs such as javascript: URIs, resulting in cross-site scripting when another user interacts with the crafted link.

## 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.