Vulnerability · Published Sep 22, 2026 · Assigned by Checkmk

CVE-2026-90990Livestatus injection via monitoring filter values

Medium 5.3

In plain English

A medium-severity security flaw in Checkmk from Checkmk GmbH. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 37% of all known vulnerabilities).

Severity (CVSS 4.0)5.3Medium

Exploit odds (30 days)0.4%top 63.4% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
Checkmk GmbH	Checkmk	2.5.0 – before 2.5.0p14

Weakness: CWE-93 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N

References

https://checkmk.com/werk/19604 vendor-advisory