CVE-2026-90990 Livestatus injection via monitoring filter values
Authenticated users can inject Livestatus headers to bypass visibility restrictions and cause resource exhaustion in Checkmk monitoring systems.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-90990?
CVE-2026-90990 is a medium-severity vulnerability in Checkmk, published on 22 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
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.
Weakness: CWE-93
Which versions are affected by CVE-2026-90990?
How do I fix CVE-2026-90990?
No fix has been published for CVE-2026-90990 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-90990 being exploited?
There is no known exploitation of CVE-2026-90990 in the wild and no public exploit code.
Sources
Also known as GHSA-v742-5hjw-gqcp.