What is CVE-2026-8833?

CVE-2026-8833 is a medium-severity vulnerability in Checkmk, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2026-06-08.

How severe is CVE-2026-8833?

Medium severity. CVSS v3 base score is 5.4 out of 10.

XSS in Checkmk

CVE-2026-8833

Improper neutralization of HTML-encoded characters in the URL validation function in Checkmk <2.5.0p5, <2.4.0p31, <2.3.0p48, and all 2.2.0 versions allows an authenticated user to bypass URL validation and inject malicious URLs such as jav…

Vulnerability class: XSS (Cross-Site Scripting)

EPSS: 0.001 (3.8th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.

Affected products

Checkmk — versions 2.2.0, 2.3.0, 2.4.0
Checkmk Gmbh — versions 2.5.0, 2.4.0, 2.3.0

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

security@checkmk.com (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2026-8833?: CVE-2026-8833 is a medium-severity vulnerability in Checkmk, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2026-06-08.
How severe is CVE-2026-8833?: Medium severity. CVSS v3 base score is 5.4 out of 10.