CVE-2026-20915

Name: CVE-2026-20915
Creator: NVD / NIST
Published: 2026-03-31T15:16:11.527+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.5/10EPSS 0.15%

Last modified Jun 17, 2026

CVE-2026-20915 is a high-severity vulnerability rated 8.5/10 on the CVSS scale. 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.. EPSS estimates a 0.15% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

5.4/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

CVSS 4.0

8.5/10

CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability

0.15%

4.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

Affected Software

Vendor	Product	Versions	Update
Checkmk	Checkmk	2.5.0	B1

References

https://checkmk.com/werk/19526Vendor Advisory

Timeline

Published: Mar 31, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-20915?

How severe is CVE-2026-20915?

CVE-2026-20915 has a CVSS score of 8.5/10 (HIGH severity). The EPSS model estimates a 0.15% probability of exploitation in the next 30 days.

How do I fix CVE-2026-20915?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-20915?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST