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CVE-2026-15576

Agent receiver accepts mTLS requests without a client certificate

MEDIUM
6.9
CVSS Score
Published: August 21, 2026 at 11:10 AM UTC
Updated: October 16, 2026 at 03:10 PM UTC
1 product affected across 1 vendorCheckmk

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Severity
MEDIUM6.9
Exploit prediction
EPSS 0.5%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Checkmk· Checkmk
90%
2.5.0 ≤ v < 2.5.0p102.5.0
Affected range stops below 2.5.0p10, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (1)

Vendor Advisory
Source: cverecord
https://checkmk.com/werk/20174

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6.9MEDIUMCheckmk
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-306

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