---
id: CVE-2026-15576
title: >-
  Improper authentication in the agent receiver of Checkmk <2.5.0p10 allows an
  unauthenticated remote attacker to bypass mutual TLS client certificate
  verification of relay endpoints by supplying a fixed placeholder identity in
  the request…
summary: >-
  Improper authentication in the agent receiver of Checkmk <2.5.0p10 allows an
  unauthenticated remote attacker to bypass mutual TLS client certificate
  verification of relay endpoints by supplying a fixed placeholder identity in
  the request…
severity: none
cwe:
  - CWE-306
published: '2026-08-21'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T15:10:00.103'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-15576'
references:
  - url: 'https://checkmk.com/werk/20174'
    label: security@checkmk.com
tags:
  - nvd
epss: 0.00453
epssPercentile: 0.39145
ingestedAt: '2026-10-27T18:52:09.906Z'
---

## Overview

Improper authentication in the agent receiver of Checkmk <2.5.0p10 allows an unauthenticated remote attacker to bypass mutual TLS client certificate verification of relay endpoints by supplying a fixed placeholder identity in the request URL, resulting in limited impact on integrity and availability. Only the Cloud, Ultimate and Ultimate MT editions are affected, as other editions do not expose relay endpoints.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.