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

6.3MediumCVSS base score
0.22%Exploitation in 30 daysEPSS · top 87% of all CVEs
NoKnown exploitednot in CISA's KEV catalog
NonePublic exploitsnone known yet

Description

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.

Timeline

2026
20 Feb 2026
20 Feb 2026
ID reserved
By Checkmk
13 Mar 202621 days later
13 Mar 2026· 21 days later
Published

Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.

Scores

CVSS scores of CVE-2026-2859, by who scored it
Scored by	CVSS	Score	Vector
CheckmkCNA (assigner)	4.0	Medium6.3	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
NVDNVD · Analyzed	4.0	Medium6.3	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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS (exploitation in 30 days): 0.22% · top 87% of all CVEs (14 Nov 2026)
CISA SSVC: Exploitation: none · Automatable: yes · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.3.

Affected products

Checkmk GmbH · Checkmk
- affected 2.4.0 – < 2.4.0p23
- affected 2.3.0 – < 2.3.0p43
- affected 2.2.0

References1

https://checkmk.com/werk/18994 (opens in a new tab)

Sources

The same CVE in the primary databases and aggregators, to check against.

Badge for a README or a ticket

[![CVE-2026-2859](https://cveledger.app/badge/CVE-2026-2859.svg)](https://cveledger.app/cve/CVE-2026-2859)

Record last updated 13 Mar 2026, 15:48 UTC.