CVE-2026-15576

Agent receiver accepts mTLS requests without a client certificate

Published Aug 21, 2026 CVSS 4.0 · 6.9 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
References
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values 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.
Title Agent receiver accepts mTLS requests without a client certificate
First Time appeared Checkmk
Checkmk checkmk
Weaknesses CWE-306
CPEs cpe:2.3:a:checkmk:checkmk:*:*:*:*:*:*:*:*
Vendors & Products Checkmk
Checkmk checkmk
References
Metrics cvssV4_0

{'score': 6.9, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
Checkmk
Published
Updated
Aug 21, 2026, 11:53 AM
Reserved
Jul 13, 2026, 8:39 AM
Status
Deferred
Published
Aug 21, 2026, 11:17 AM
Modified
Oct 16, 2026, 3:10 PM