CVE-2026-8833 PUBLISHED

XSS in urls

Assigner: Checkmk
Reserved: 18.05.2026 Published: 08.06.2026 Updated: 08.06.2026

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.

Metrics

CVSS 4.0

CVSS Vector: 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
CVSS Score: 8.5

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	High	Confidentiality	None
Attack Complexity	Low	Integrity	High	Integrity	Low
Attack Requirements	None	Availability	High	Availability	None
Privileges Required	Low
User Interaction	Active

CVSS 4.0

Product Status

Vendor	Checkmk GmbH
Product	Checkmk
Versions	Default: unaffected affected from 2.5.0 to 2.5.0p5 (excl.) affected from 2.4.0 to 2.4.0p31 (excl.) affected from 2.3.0 to 2.3.0p48 (excl.) Version 2.2.0 is affected

Credits

Arvato Systems Offensive Security reporter

References

https://checkmk.com/werk/20002

Problem Types

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') CWE

Impacts

CAPEC-63: Cross-Site Scripting (XSS)