High severity · published Oct 30, 2025
CVE-2025-39663
Cross Site Scripting through compromised remote site
8.4
CVSS
0.6%
EPSS
No
On KEV
Description
Cross-Site Scripting (XSS) vulnerability in Checkmk's distributed monitoring allows a compromised remote site to inject malicious HTML code into service outputs in the central site. Affecting Checkmk before 2.4.0p14, 2.3.0p39, 2.2.0 and 2.1.0 (eol).
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
High
User interaction
Required
Confidentiality
High
Integrity
High
Availability
High
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.6% · higher than 49% 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 2.4.0p14; 2.3.0 before 2.3.0p39; 2.2.0; 2.1.0 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-39663
CVE.org
https://www.cve.org/CVERecord?id=CVE-2025-39663
Vendor Advisory
https://checkmk.com/werk/17998
Exploit
https://github.com/sbaresearch/advisories/tree/82fd27e4570433464c30b35150b197db9a850f4e/2025/SBA-ADV-20250729-01_Checkmk_Cross_Site_Scripting
Exploit
http://seclists.org/fulldisclosure/2025/Nov/0
More from Checkmk
9.8
CVE-2024-28825
Brute-force protection ineffective for some login methods
8.8
CVE-2026-24096
Insufficient permission validation on multiple REST API Quick Setup endpoints
8.8
CVE-2025-32918
Livestatus injection in autocomplete endpoint
8.8
CVE-2025-1712
Arbitrary file write with vcrtrace
8.8
CVE-2025-32917
Privilege escalation in jar_signature