Medium severity · published Feb 26, 2026
CVE-2025-64999
Cross-site scripting in HTML logs of Synthetic Monitoring test services
5.4
CVSS
0.2%
EPSS
No
On KEV
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 vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
Required
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 6% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CH
Checkmk · Checkmk GmbH
2.4.0 before 2.4.0p22; 2.3.0 before 2.3.0p43 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-64999
CVE.org
https://www.cve.org/CVERecord?id=CVE-2025-64999
Vendor Advisory
https://checkmk.com/werk/19238
github.com
https://github.com/sbaresearch/advisories/tree/e72ce9bb6b9ffffc1fc35e4d8152ad153293c851/2025/SBA-ADV-20251118-01_Checkmk_Cross_Site_Scripting
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