What is CVE-2026-2859?

CVE-2026-2859 is a medium-severity vulnerability in Checkmk, classified under Observable Response Discrepancy. CVSS score: 4.3/10. Published 2026-03-13.

How severe is CVE-2026-2859?

Medium severity. CVSS v3 base score is 4.3 out of 10.

Vulnerability in Checkmk

CVE-2026-2859

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.

EPSS: 0.002 (9.0th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N.

Affected products

Checkmk — versions 2.2.0, 2.3.0, 2.4.0
Checkmk Gmbh — versions 2.4.0, 2.3.0, 2.2.0

Weakness classification (CWE)

CWE-204 — Observable Response Discrepancy

References

security@checkmk.com (Vendor Advisory)

Frequently asked questions

What is CVE-2026-2859?: CVE-2026-2859 is a medium-severity vulnerability in Checkmk, classified under Observable Response Discrepancy. CVSS score: 4.3/10. Published 2026-03-13.
How severe is CVE-2026-2859?: Medium severity. CVSS v3 base score is 4.3 out of 10.