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CVE-2026-90990

Livestatus injection via monitoring filter values

MEDIUM
5.3
CVSS Score
Published: September 22, 2026 at 10:43 AM UTC
Updated: September 22, 2026 at 02:17 PM UTC
1 product affected across 1 vendorCheckmk

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Severity
MEDIUM5.3
Exploit prediction
EPSS 0.4%
SSVC
No known exploit

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Checkmk· Checkmk
95%
2.5.0 ≤ v < 2.5.0p142.5.0
Affected range stops below 2.5.0p14, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (1)

Vendor Advisory
Source: cverecord
https://checkmk.com/werk/19604

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.3MEDIUMCheckmk
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-93

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