CVE-2025-64999 PUBLISHED

Cross-site scripting in HTML logs of Synthetic Monitoring test services

Assigner: Checkmk
Reserved: 12.11.2025 Published: 26.02.2026 Updated: 26.02.2026

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.

Metrics

CVSS 4.0

CVSS Vector: 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
CVSS Score: 7.3

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	High	Confidentiality	None
Attack Complexity	Low	Integrity	High	Integrity	Low
Attack Requirements	Present	Availability	High	Availability	None
Privileges Required	Low
User Interaction	Active

CVSS 4.0

Product Status

Vendor	Checkmk GmbH
Product	Checkmk
Versions	Default: unaffected affected from 2.4.0 to 2.4.0p22 (excl.) affected from 2.3.0 to 2.3.0p43 (excl.)

Credits

Lisa Gnedt (SBA Research) reporter

References

https://checkmk.com/werk/19238

Problem Types

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') CWE

Impacts

CAPEC-592: Stored XSS