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Vulnerability record · CVE-2026-9549 · published 8 June 2026

CVE-2026-9549: Checkmk cross-site scripting vulnerability

Checkmk · Checkmk

Stored cross-site scripting in the service discovery active check output in Checkmk <2.5.0p5, <2.4.0p31, <2.3.0p48, and all 2.2.0 versions allows an administrator who can configure active or custom checks to inject malicious HTML or JavaScript into check output that executes in the browser of an admin or a user with host read permissions when they run the check on the service discovery page.

4.8 CVSS 4.0 Medium EPSS 0.24% · top 86.2% CWE-79 · Cross-site scripting
4.8CVSS 4.0 base score
0.24%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
1References
23 Jul 2026Last modified by NVD

Description

Stored cross-site scripting in the service discovery active check output in Checkmk <2.5.0p5, <2.4.0p31, <2.3.0p48, and all 2.2.0 versions allows an administrator who can configure active or custom checks to inject malicious HTML or JavaScript into check output that executes in the browser of an admin or a user with host read permissions when they run the check on the service discovery page.

CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:N/VI:L/VA:N/SC:N/SI:L/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:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://checkmk.com/werk/17993 Vendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2024-28825Checkmk improper restriction of authentication attempts vulnerabilityImproper restriction of excessive authentication attempts on some authentication methods in Checkmk before 2.3.0b5 (beta), 2.2.0p26, 2.1.0p43, and in…EPSS 0.52%9.8CVE-2022-48317Checkmk insufficient session expiration vulnerabilityExpired sessions were not securely terminated in the RestAPI for Tribe29's Checkmk <= 2.1.0p10 and Checkmk <= 2.0.0p28 allowing an attacker to use ex…EPSS 0.46%9.3CVE-2025-39666Checkmk untrusted search path vulnerabilityLocal privilege escalation in Checkmk 2.2.0 (EOL), Checkmk 2.3.0 before 2.3.0p46, Checkmk 2.4.0 before 2.4.0p25, and Checkmk 2.5.0 (beta) before 2.5.…EPSS 0.12%9.2CVE-2024-8606Checkmk incorrect authorization vulnerabilityBypass of two factor authentication in RestAPI in Checkmk < 2.3.0p16 and < 2.2.0p34 allows authenticated users to bypass two factor authenticationEPSS 0.46%8.8CVE-2025-32919Checkmk uncontrolled search path element vulnerabilityUse of an insecure temporary directory in the Windows License plugin for the Checkmk Windows Agent allows Privilege Escalation. This issue affects Ch…EPSS 0.27%8.8CVE-2024-28828Checkmk cross-site request forgery vulnerabilityCross-Site request forgery in Checkmk < 2.3.0p8, < 2.2.0p29, < 2.1.0p45, and <= 2.0.0p39 (EOL) could lead to 1-click compromize of the site.EPSS 0.25%8.8CVE-2023-6156Checkmk vulnerabilityImproper neutralization of livestatus command delimiters in the availability timeline in Checkmk <= 2.0.0p39, < 2.1.0p37, and < 2.2.0p15 allows arbit…EPSS 0.86%8.8CVE-2023-6157Checkmk vulnerabilityImproper neutralization of livestatus command delimiters in ajax_search in Checkmk <= 2.0.0p39, < 2.1.0p37, and < 2.2.0p15 allows arbitrary livestatu…EPSS 0.89%

Source: NIST National Vulnerability Database (record CVE-2026-9549), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.