How severe is CVE-2025-39663?

CVE-2025-39663 has a CVSS 3.x base score of 8.4, rated high severity. It is exploitable over network with low attack complexity, requires high privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2025-39663 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (42nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-39663?

CVE-2025-39663 primarily affects Checkmk. In total, 53 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2025-39663?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2025-39663 have an EU (EUVD) identifier?

Yes. CVE-2025-39663 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-36997.

When was CVE-2025-39663 published?

CVE-2025-39663 was published on 2025-10-30 and last updated on 2026-06-17.

CVE-2025-39663

CVE-2025-39663 is a high-severity vulnerability in Checkmk with a CVSS 3.x base score of 8.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.

Key facts

Severity: High (CVSS 3.x base score 8.4)
CVSS v4: 8.5
EPSS exploit prediction: 1% (42nd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-36997
Weakness: CWE-79
Affected product: Checkmk
Published: 2025-10-30
Last modified: 2026-06-17

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).

Frequently asked questions

What is 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).
How severe is CVE-2025-39663?: CVE-2025-39663 has a CVSS 3.x base score of 8.4, rated high severity. It is exploitable over network with low attack complexity, requires high privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2025-39663 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (42nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-39663?: CVE-2025-39663 primarily affects Checkmk. In total, 53 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2025-39663?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2025-39663 have an EU (EUVD) identifier?: Yes. CVE-2025-39663 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-36997.
When was CVE-2025-39663 published?: CVE-2025-39663 was published on 2025-10-30 and last updated on 2026-06-17.

References

Affected products (53)

cpe:2.3:a:checkmk:checkmk:*:*:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:-:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p1:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p10:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p11:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p12:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p13:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p14:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p15:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p16:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p17:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p18:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p19:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p2:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p20:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p21:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p22:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p23:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p24:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p25:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p26:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p27:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p28:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p29:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p3:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p30:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p31:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p32:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p33:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p34:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p35:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p36:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p37:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p38:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p4:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p5:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p6:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p7:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p8:*:*:*:*:*:*
cpe:2.3:a:checkmk:checkmk:2.3.0:p9:*:*:*:*:*:*

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