# CVE-2026-90990: Checkmk Livestatus injection in monitoring filter values

Source: https://junglewise.ai/threats/cve-2026-90990-improper-neutralization-of-newlines-in-filter-values-in-the  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-22. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-90990 · Severity: info · Published 2026-09-22

Checkmk is a monitoring and alerting platform that tracks the health of IT infrastructure. An authenticated user can inject specially crafted filter values into the monitoring API to bypass visibility restrictions, view information about hosts and services they shouldn't have access to, and exhaust server resources by keeping workers occupied indefinitely.

Technologies: [Checkmk](https://junglewise.ai/threats/technologies/checkmk). Vendors: [Checkmk](https://junglewise.ai/threats/vendors/checkmk).

## Quick answers

**Is CVE-2026-90990 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-90990 being exploited in the wild.

**How severe is CVE-2026-90990?** Informational severity, published 22 September 2026.

**Which products and versions are affected?** Checkmk 2.5.0 before 2.5.0p14, 3.0.0 before 3.0.0b1.

**Is there a fix for CVE-2026-90990?** A patch was published on 2026-09-04. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-90990 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-90990?** Check whether you run Checkmk at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

Improper neutralization of newlines in filter values in the monitoring host and service list APIs allows authenticated users to inject additional Livestatus query headers through crafted filter parameters. This enables bypassing object visibility restrictions based on contact groups in count queries and injecting wait headers to tie up web server and Livestatus worker processes for an attacker-controlled duration.

## Affected products

- Checkmk Checkmk 2.5.0 before 2.5.0p14, 3.0.0 before 3.0.0b1

## Timeline

- 2026-09-22: disclosed
- 2026-09-04: patched

## References

- [https://checkmk.com/werk/19604](https://checkmk.com/werk/19604)

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