Medium severity · published Aug 21, 2026
CVE-2026-15576
Agent receiver accepts mTLS requests without a client certificate
6.9
CVSS
0.5%
EPSS
No
On KEV
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.
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 39% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CH
Checkmk · Checkmk GmbH
2.5.0 before 2.5.0p10 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-15576
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-15576
checkmk.com
https://checkmk.com/werk/20174
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