Vulnerability in Checkmk's distributed monitoring (CVE-2025-39663)
Summary
Vulnerability in Checkmk's distributed monitoring (CVE-2025-39663). Successful exploitation can lead to full system takeover.
Original description
The description as published by the source.
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).
Source: NIST National Vulnerability Database NVD
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2025-39663 has been found in Checkmk's distributed monitoring.
Successful exploitation can lead to full system takeover. CVSS score: 8.4/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Checkmk's distributed monitoring CVE-2025-39663" on the vendor's site.
CVE-2025-39663 (Checkmk's distributed monitoring) — CWE-80 / CVSS v3 8.4
Attack vector: remote (network-reachable)
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-80) exists in Checkmk's distributed monitoring.
Check the vendor advisory for the affected versions of Checkmk's distributed monitoring.
Severity: High (CVSS 8.4/10). Successful exploitation can lead to full system takeover.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで Checkmk's distributed monitoring を使っているサービスとバージョンを洗い出す。
-
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
References
- exploit github.com
- exploit seclists.org
- patch security@checkmk.com