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).

CVSS 8.5 · High

External lookup

Potential internet exposure

Potential exposure only — not proof of vulnerability.Shodan results indicate potentially internet-exposed products, not confirmed vulnerable systems. They do not confirm that any returned system is vulnerable to CVE-2025-39663.

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Product CPE queries

Derived from this CVE's existing NVD CPE 2.3 records; the application, operating-system, or hardware part is retained.

cpe:2.3:a:checkmk:checkmkSearch this product on Shodan

Exact CVE query

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Metadata

Canonical fields

NVD status

Unavailable

Published

Oct 30, 2025

Modified

Jun 17, 2026

Official record

Authoritative NVD record

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CWE IDs

Vendor classifications

How this vector reads

CVSS 4.0 base metrics decoded below. This explanation does not recalculate or change the NVD score.

Attack Vector (AV): Network. The vulnerable system can be reached across network boundaries.
Attack Complexity (AC): Low. No special conditions beyond the attacker-controlled steps are required.
Attack Requirements (AT): None. No prerequisite deployment or execution condition is required.
Privileges Required (PR): High. The attacker needs significant administrative privileges.
User Interaction (UI): Passive. A targeted user must unknowingly interact with the vulnerable system.
Vulnerable System Confidentiality (VC): High. There is a total or serious impact to this security property.
Vulnerable System Integrity (VI): High. There is a total or serious impact to this security property.
Vulnerable System Availability (VA): High. There is a total or serious impact to this security property.
Subsequent System Confidentiality (SC): None. There is no direct impact to this security property.
Subsequent System Integrity (SI): None. There is no direct impact to this security property.
Subsequent System Availability (SA): None. There is no direct impact to this security property.

Optional CVSS v4 metrics remain in the raw vector; only base metrics are expanded here.

Signals

Exploitation indicators

0 stored signals · no KEV · 0 OTX pulses