CVE-2026-90990Network attack vectorHinoki check available

Monitoring disclosure via Livestatus header injection

Published Sep 22, 2026 · Updated Sep 22, 2026

Livestatus injection in Checkmk 2.5.0 before 2.5.0p14 allows remote authenticated users to infer restricted monitoring data. The monitoring host and service list APIs insert newline-bearing filter values into Livestatus queries, creating attacker-supplied headers and request boundaries. Any authenticated account can bypass contact-group visibility in count queries or hold web and Livestatus workers for a chosen duration.

CVSS severity5.3
Medium
EPSS probability0.42%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Livestatus injection in Checkmk 2.5.0 before 2.5.0p14 allows remote authenticated users to infer restricted monitoring data. The monitoring host and service list APIs insert newline-bearing filter values into Livestatus queries, creating attacker-supplied headers and request boundaries. Any authenticated account can bypass contact-group visibility in count queries or hold web and Livestatus workers for a chosen duration.

The record

CVE
CVE-2026-90990
Published
Sep 22, 2026
Updated
Sep 22, 2026
Vendor
Checkmk GmbH
Product
Checkmk
Classifications
T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 22, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 22, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.5.0 <2.5.0p14

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Checkmk GmbH · Checkmkversion=2.5.0 <2.5.0p14

Published CVSS scores

5.3Checkmk GmbHCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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