CVE-2026-20915
Received Received - Intake
Stored XSS in Checkmk Pending Changes Sidebar Allows Script Injection

Publication date: 2026-03-31

Last updated on: 2026-04-02

Assigner: Checkmk GmbH

Description
Stored cross-site scripting (XSS) in Checkmk version 2.5.0 (beta) before 2.5.0b2 allows authenticated users with permission to create pending changes to inject malicious JavaScript into the Pending Changes sidebar, which will execute in the browsers of other users viewing the sidebar.
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Meta Information
Published
2026-03-31
Last Modified
2026-04-02
Generated
2026-06-16
AI Q&A
2026-03-31
EPSS Evaluated
2026-06-15
NVD
CVE-2026-20915
EUVD
EUVD-2026-17417
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
checkmk checkmk 2.5.0
Helpful Resources
Exploitability
CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-79 The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
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Executive Summary

CVE-2026-20915 is a stored cross-site scripting (XSS) vulnerability found in the Pending Changes sidebar of Checkmk versions 2.5.0 and 2.6.0b1. Authenticated users who have permission to create pending changes can inject malicious JavaScript code into change attributes because these inputs are not properly sanitized before being displayed. When other users view the Pending Changes sidebar, the malicious script executes in their browsers, potentially compromising their security.

Impact Analysis

This vulnerability can lead to malicious JavaScript executing in the browsers of users who view the Pending Changes sidebar. This can result in unauthorized actions being performed on behalf of those users, theft of sensitive information such as session cookies, or other malicious activities that compromise user accounts and system integrity.

Mitigation Strategies

The vulnerability has been fixed in the Werk #19526 update for Checkmk versions 2.5.0 and 2.6.0b1 across all editions.

To mitigate this vulnerability, you should update your Checkmk installation to the fixed version as provided in the Werk #19526 update.

The fix requires no manual interaction and maintains compatibility with existing configurations.

Compliance Impact

The provided information does not specify how the stored cross-site scripting (XSS) vulnerability in Checkmk affects compliance with common standards and regulations such as GDPR or HIPAA.

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