CVE-2025-39663

Name: CVE-2025-39663
Creator: NVD / NIST
Published: 2025-10-30T11:15:32.4+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.5/10EPSS 0.56%

Last modified Jun 17, 2026

CVE-2025-39663 is a high-severity vulnerability rated 8.5/10 on the CVSS scale. 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).. EPSS estimates a 0.56% chance of exploitation in the next 30 days.

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).

Metrics

CVSS 3.1

8.4/10

CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:H

CVSS 4.0

8.5/10

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

EPSS Probability

0.56%

42.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Checkmk	Checkmk	>= 2.0.0, < 2.3.0
Checkmk	Checkmk	2.3.0
Checkmk	Checkmk	2.4.0

References

https://checkmk.com/werk/17998Vendor Advisory
https://github.com/sbaresearch/advisories/tree/82fd27e4570433464c30b35150b197db9a850f4e/2025/SBA-ADV-20250729-01_Checkmk_Cross_Site_ScriptingExploit, Third Party Advisory
http://seclists.org/fulldisclosure/2025/Nov/0Exploit, Mailing List, Third Party Advisory
https://github.com/sbaresearch/advisories/tree/82fd27e4570433464c30b35150b197db9a850f4e/2025/SBA-ADV-20250729-01_Checkmk_Cross_Site_ScriptingExploit, Third Party Advisory

Timeline

Published: Oct 30, 2025
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2025-39663?

How severe is CVE-2025-39663?

CVE-2025-39663 has a CVSS score of 8.5/10 (HIGH severity). The EPSS model estimates a 0.56% probability of exploitation in the next 30 days.

How do I fix CVE-2025-39663?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2025-39663?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST