CVE-2026-15576: CWE-306: Missing Authentication for Critical Function in Checkmk GmbH Checkmk
Description
CVE-2026-15576 is a medium severity vulnerability in Checkmk versions 2.5.0 through 2.5.0p9. It involves improper authentication in the agent receiver component, allowing an unauthenticated remote attacker to bypass mutual TLS client certificate verification on relay endpoints by using a fixed placeholder identity in the request URL. This issue affects only the Cloud, Ultimate, and Ultimate MT editions of Checkmk, as other editions do not expose relay endpoints. The impact is limited to integrity and availability.
CVSS v4.0
Score 6.9medium
Affected software
Checkmk GmbH
Checkmk
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-15576 describes a missing authentication vulnerability (CWE-306) in Checkmk agent receiver before version 2.5.0p10. An unauthenticated remote attacker can bypass mutual TLS client certificate verification of relay endpoints by supplying a fixed placeholder identity in the request URL. This bypass allows limited impact on the integrity and availability of the affected system. The vulnerability affects only the Cloud, Ultimate, and Ultimate MT editions of Checkmk, as other editions do not expose relay endpoints.
Potential Impact
The vulnerability allows unauthenticated remote attackers to bypass mutual TLS client certificate verification on relay endpoints, potentially impacting the integrity and availability of the affected Checkmk installations. The impact is limited and does not affect confidentiality. Only specific editions (Cloud, Ultimate, Ultimate MT) are affected.
Mitigation Recommendations
A fix is available in Checkmk version 2.5.0p10. Users should upgrade to version 2.5.0p10 or later to remediate this vulnerability. Since this is an on-premises product, administrators must apply the update manually. No other mitigation steps are indicated.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- Checkmk
- Date Reserved
- 2026-07-13T08:39:03.953Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6a883514acd9273b490dfd68
Added to database: 08/21/2026, 11:23:00 UTC
Last enriched: 09/11/2026, 03:03:22 UTC
Last updated: 10/05/2026, 18:48:17 UTC
Views: 72
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