CVE-2026-90990
Medium
Description
Improper neutralization of newlines in filter values in the monitoring host and service list APIs in Checkmk <2.5.0p14 allows an authenticated user to inject additional Livestatus query headers, bypassing object visibility restrictions in count queries to infer information about hosts and services outside their contact groups and occupying web server and Livestatus workers for an attacker-controlled duration.
SeverityMedium
CVSS5.3
Exploit probability—
ProductCheckmk
PublishedSep 22, 2026
First seenSep 22, 2026
Weakness typeCWE-93CWE-93
How to fix
Update
- Checkmk GmbH Checkmk2.5.0p14 or later
Vendor advisories
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| Checkmk GmbH Checkmk | 2.5.0 ≤ v < 2.5.0p14 | 2.5.0p14 |
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