What is CVE-2026-9549?

CVE-2026-9549 is a medium-severity vulnerability in Checkmk, classified under Cross-site Scripting. CVSS score: 4.8/10. Published 2026-06-08.

How severe is CVE-2026-9549?

Medium severity. CVSS v3 base score is 4.8 out of 10.

XSS in Checkmk

CVE-2026-9549

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 JavaSc…

Vulnerability class: XSS (Cross-Site Scripting)

CVSS v3 metric

CVSS v3 base score 4.8 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N.

Affected products

Checkmk — versions 2.2.0, 2.3.0, 2.4.0

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

security@checkmk.com (Vendor Advisory)

Frequently asked questions

What is CVE-2026-9549?: CVE-2026-9549 is a medium-severity vulnerability in Checkmk, classified under Cross-site Scripting. CVSS score: 4.8/10. Published 2026-06-08.
How severe is CVE-2026-9549?: Medium severity. CVSS v3 base score is 4.8 out of 10.