CVE-2026-9549

What it is

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 JavaScript into check output that executes in the browser of an admin or a user with host read permissions when they run the check on the service discovery page.

At a glance

Exploitability

Can be exploited over the network with an admin-level account, but needs a user to act. Limited direct impact.

Exploit odds

0.1% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-06-08 13:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-23 22:10 UTC Last updatedMost recent change to the record

Details

Published

2026-06-08 13:16 UTC

Last modified

2026-10-23 22:10 UTC

Exploit probability

0.1% · EPSS, next 30 days

Weakness

CWE-79 · Cross-site scripting

Record status

Analyzed

Affected

• Checkmk 2.2.0
• Checkmk 2.3.0
• Checkmk 2.4.0
• Checkmk 2.5.0

Attack profile CVSS 4.0 · 4.8

Attack vector

Network

Complexity

Low

Attack requirements

None

Privileges needed

High

User interaction

Passive

Confidentiality

None

Integrity

Low

Availability

None