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Vulnerability record · CVE-2025-64999 · published 26 February 2026

CVE-2025-64999: Checkmk cross-site scripting vulnerability

Checkmk · Checkmk

Improper neutralization of input in Checkmk versions 2.4.0 before 2.4.0p22, and 2.3.0 before 2.3.0p43 allows an attacker that can manipulate a host's check output to inject malicious JavaScript into the Synthetic Monitoring HTML logs, which can then be accessed via a crafted phishing link.

7.3 CVSS 4.0 High EPSS 0.15% · top 96.7% CWE-79 · Cross-site scripting
7.3CVSS 4.0 base score
0.15%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References
17 Jun 2026Last modified by NVD

Description

Improper neutralization of input in Checkmk versions 2.4.0 before 2.4.0p22, and 2.3.0 before 2.3.0p43 allows an attacker that can manipulate a host's check output to inject malicious JavaScript into the Synthetic Monitoring HTML logs, which can then be accessed via a crafted phishing link.

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:A/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:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://checkmk.com/werk/19238 Vendor Advisory
https://github.com/sbaresearch/advisories/tree/e72ce9bb6b9ffffc1fc35e4d8152ad153293c851/2025/SBA-ADV-20251118-01_Checkmk

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2025-64999), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.