XSS in Checkmk
CVE-2025-39663
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).
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.4 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.006 (44.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 45th percentile — 44.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: 0.000
Affected products
- Checkmk — versions 2.3.0, 2.4.0
- Checkmk Gmbh — versions 2.4.0, 2.3.0, 2.2.0
Weakness classification (CWE)
References
- checkmk.com/werk/17998 (Vendor Advisory)
- github.com/sbaresearch/advisories/tree/82fd27e4570433464c30b35150b197db9a850f4e… (Exploit, Third Party Advisory)
- af854a3a-2127-422b-91ae-364da2661108 (Exploit, Mailing List, Third Party Advisory)
Frequently asked questions
- What is CVE-2025-39663?
- CVE-2025-39663 is a high-severity vulnerability in Checkmk, classified under Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS). CVSS score: 8.4/10. Published 2025-10-30.
- How severe is CVE-2025-39663?
- High severity. CVSS v3 base score is 8.4 out of 10.