XSS in urls
CVE-2026-8833

8.5HIGH

Key Information:

Vendor

Checkmk Gmbh

Status
Checkmk
Vendor
CVE Published:
8 June 2026

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

Affected Version(s)

Checkmk 2.5.0 < 2.5.0p5

Checkmk 2.4.0 < 2.4.0p31

Checkmk 2.3.0 < 2.3.0p48

References

https://checkmk.com/werk/20002
vendor-advisory

CVSS V4

Score:
8.5
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
Unknown

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Arvato Systems Offensive Security
.