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CVE-2025-39663

Checkmk cross-site scripting (XSS)

8.4 HIGHPublic exploitEPSS 0.60%
  1. Published30 Oct 2025

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 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredHigh
User interactionRequired
ScopeChanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:H

Affected products

Checkmk≥ 2.0.0 < 2.3.0 · 2.3.0 · 2.4.0

Remediation

Fixed in
Checkmk≥ 2.3.0
Patch & vendor advisories

References

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Frequently asked

Is CVE-2025-39663 being actively exploited?

CVE-2025-39663 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.60%.

How severe is CVE-2025-39663?

CVE-2025-39663 has a CVSS 3.1 base score of 8.4, rated high. EPSS estimates a 0.60% probability of exploitation.

Which products are affected by CVE-2025-39663?

Affected products include Checkmk.

How do I fix CVE-2025-39663?

Upgrade affected software to a fixed version, for example Checkmk 2.3.0 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2025-39663 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.