Medium 6.3Published Mar 13, 2026

CVE-2026-2859Unauthenticated Host Enumeration via Observable Response Discrepancy on Deploy Agent Endpoint

Updated under an hour ago (Oct 26, 2026, 10:00 PM ET)

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It affects Checkmk GmbH Checkmk. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for Checkmk GmbH Checkmk

Exploited in the last 30 days

Improper permission enforcement in Checkmk versions 2.4.0 before 2.4.0p23, 2.3.0 before 2.3.0p43, and 2.2.0 (EOL) allows unauthenticated users to enumerate existing hosts by observing different HTTP response codes in deploy_agent endpoint, which could lead to information disclosure.

CVSS: 6.3 MEDIUM (v4.0, CNA)CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
Weakness (CWE): CWE-204
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Checkmk
NVD analysis: Analyzed
Record last updated: Mar 13, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Checkmk GmbH Checkmk checkmk:checkmk (from the name)	from 2.4.0 before 2.4.0p23; from 2.3.0 before 2.3.0p43; 2.2.0	CNA record
checkmk checkmk checkmk:checkmk	2.2.0; 2.2.0; 2.2.0; 2.2.0; 2.2.0; 2.2.0; 2.2.0; 2.2.0; and 127 more ranges	NVD

References

References

https://checkmk.com/werk/18994	vendor-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.