Vulnerability · Published Mar 13, 2026 · Assigned by Checkmk
CVE-2026-2859Unauthenticated Host Enumeration via Observable Response Discrepancy on Deploy Agent Endpoint
Medium 6.3
In plain English
A medium-severity security flaw in Checkmk from Checkmk GmbH. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 10% of all known vulnerabilities).
Severity (CVSS 4.0)6.3Medium
Exploit odds (30 days)0.2%top 89.8% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official 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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Checkmk GmbH | Checkmk | 2.4.0 – before 2.4.0p232.3.0 – before 2.3.0p432.2.0 |
Weakness: CWE-204 · Vector: 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