CVE-2026-15937Network attack vectorHinoki check available

Cross-endpoint authentication via mismatched certificate roots

Published Sep 4, 2026 · Updated Sep 4, 2026

Improper certificate validation in Checkmk 2.5.0 before 2.5.0p10 allows remote authenticated users to cross-authenticate receiver endpoints. The agent receiver accepts an mTLS certificate without verifying that its issuer is the root assigned to the requested relay or push-agent endpoint. Exploitation requires a relay and registered push agent with the same UUID, enabling either certificate to access the other endpoint.

CVSS severity5.3
Medium
EPSS probability0.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Improper certificate validation in Checkmk 2.5.0 before 2.5.0p10 allows remote authenticated users to cross-authenticate receiver endpoints. The agent receiver accepts an mTLS certificate without verifying that its issuer is the root assigned to the requested relay or push-agent endpoint. Exploitation requires a relay and registered push agent with the same UUID, enabling either certificate to access the other endpoint.

The record

CVE
CVE-2026-15937
Published
Sep 4, 2026
Updated
Sep 4, 2026
Vendor
Checkmk GmbH
Product
Checkmk
Classifications
CWE-295, CAPEC-114, T1550
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 4, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 4, 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 <2.5.0p10

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Checkmk GmbH · Checkmkversion=2.5.0 <2.5.0p10

Published CVSS scores

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

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

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-295Improper Certificate Validation
CAPEC-114Authentication Abuse
T1550Use Alternate Authentication Material

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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