8.5

CVE-2026-20915: checkmk gmbh checkmk Cross-site Scripting

CVSS: 8.5v4.0HighAnalyzed
AliasesUBUNTU-CVE-2026-20915
Published 31-03-2026Last modified 31-03-2026
Open JSON

Vulnerability summary

CVE-2026-20915 is a high (CVSS 8.5) Cross-site Scripting vulnerability in checkmk gmbh checkmk. EPSS estimates a 0.15% chance of exploitation in the next 30 days, higher than 3.5% of scored vulnerabilities.

Overall risk
34/100
0100
Medium · default modelHow is this calculated?
CVSS score
8.5/10
010
High · v4.0 (CVE.org)
EPSS score
0.15%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 31-03-2026
    PublishedVulnerability first disclosed.
  2. 31-03-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

5 scores · 3 sources · 2 versions

EPSS trend

Probability

0.15%

Chance of exploitation in the next 30 days

Percentile

4%

Versus all other CVEs

30-day change

0.00 pp

From 0.15% on 21-09-2026

21-09-202621-10-2026
EPSS score
0.15%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Checkmk1 product
Checkmk gmbh1 product
Ubuntu1 product
  • check-mkAll versions (No fix recorded)

3 vendors · 3 products

References

3 links