CVE-2026-15576
Agent receiver accepts mTLS requests without a client certificate
Description
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.
INFO
Published Date :
Aug. 21, 2026, 11:17 a.m.
Last Modified :
Oct. 16, 2026, 3:10 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update Checkmk to version 2.5.0p10 or later.
- Verify relay endpoint configurations.
- Ensure mutual TLS is correctly enforced.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-15576.
| URL | Resource |
|---|---|
| https://checkmk.com/werk/20174 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-15576 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-15576
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-15576 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-15576 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Translated by [email protected]
Oct. 16, 2026
Action Type Old Value New Value Changed Translation Title: Checkmk GmbH, Description: Autenticación incorrecta en el receptor del agente de Checkmk menor que 2.5.0p10 permite a un atacante remoto no autenticado eludir la verificación mutua de certificados de cliente TLS de los puntos finales de retransmisión al proporcionar una identidad de marcador de posición fija en la URL de la solicitud, lo que resulta en un impacto limitado en la integridad y la disponibilidad. Solo las ediciones Cloud, Ultimate y Ultimate MT se ven afectadas, ya que otras ediciones no exponen puntos finales de retransmisión. Title: Checkmk GmbH, Description: Autenticación incorrecta en el receptor del agente de Checkmk menor que 2.5.0p10 permite a un atacante remoto no autenticado eludir la verificación mutua de certificados de cliente TLS de los puntos finales de retransmisión al proporcionar una identidad de marcador de posición fija en la URL de la solicitud, lo que resulta en un impacto limitado en la integridad y la disponibilidad. Solo las ediciones Cloud, Ultimate y Ultimate MT se ven afectadas, ya que otras ediciones no exponen puntos finales de retransmisión. -
CVE Translated by [email protected]
Oct. 16, 2026
Action Type Old Value New Value Added Translation Title: Checkmk GmbH, Description: Autenticación incorrecta en el receptor del agente de Checkmk menor que 2.5.0p10 permite a un atacante remoto no autenticado eludir la verificación mutua de certificados de cliente TLS de los puntos finales de retransmisión al proporcionar una identidad de marcador de posición fija en la URL de la solicitud, lo que resulta en un impacto limitado en la integridad y la disponibilidad. Solo las ediciones Cloud, Ultimate y Ultimate MT se ven afectadas, ya que otras ediciones no exponen puntos finales de retransmisión. -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Aug. 21, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-15576', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-08-21T11:53:35.618102Z'} -
New CVE Received by [email protected]
Aug. 21, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'Checkmk GmbH', 'product': 'Checkmk', 'versions': [{'status': 'affected', 'version': '2.5.0', 'lessThan': '2.5.0p10', 'versionType': 'semver'}], 'defaultStatus': 'unaffected'}] Added Description 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. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-306 Added Reference https://checkmk.com/werk/20174