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Vulnerability record · CVE-2026-8833 · published 8 June 2026

CVE-2026-8833: Checkmk cross-site scripting vulnerability

Checkmk · Checkmk

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 javascript: URIs, resulting in cross-site scripting when another user interacts with the crafted link.

8.5 CVSS 4.0 High EPSS 0.24% · top 86.6% CWE-79 · Cross-site scripting
8.5CVSS 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

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 javascript: URIs, resulting in cross-site scripting when another user interacts with the crafted link.

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:H/VA:H/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/20002 Vendor Advisory

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Related vulnerabilities

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

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Source: NIST National Vulnerability Database (record CVE-2026-8833), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.