Executive brief
Checkmk is an IT infrastructure monitoring platform. A security flaw in its search feature allows an authorized user to create specially named monitoring targets (hosts or services) that contain malicious code. If another administrator or user searches for these items, the malicious code will run in their browser, potentially allowing the attacker to steal session information or perform actions on their behalf.
Technical details
A stored cross-site scripting (XSS) vulnerability exists in the Unified Search feature of Checkmk. The root cause is the failure to properly sanitize host and service names before rendering them in search results. An authenticated attacker with permissions to create or modify hosts/services can inject malicious JavaScript into these object names. When another user performs a search that returns these objects, the payload executes in their browser context. This vulnerability was addressed in version 2.5.0b2.
Affected products
- Checkmk GmbH Checkmk 2.5.0 (beta) before 2.5.0b2
Timeline
- 2026-03-23: patched: Fix released in version 2.5.0b2
- 2026-03-31: disclosed: Initial advisory publication