CVE-2026-2859 Unauthenticated Host Enumeration via Observable Response Discrepancy on Deploy Agent Endpoint
Unauthenticated attackers can enumerate existing hosts by observing response discrepancies in the deploy agent endpoint, leading to information disclosure.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-2859?
CVE-2026-2859 is a medium-severity vulnerability in Checkmk Checkmk, published on 13 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Weakness: CWE-204
Which versions are affected by CVE-2026-2859?
It affects 1 product.
Products include Checkmk Checkmk.
How do I fix CVE-2026-2859?
No fix has been published for CVE-2026-2859 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-2859 being exploited?
There is no known exploitation of CVE-2026-2859 in the wild and no public exploit code.
Other vulnerabilities in Checkmk Checkmk
- CVE-2025-39666 omd: Local privilege escalation when executing omd commands as root
- CVE-2024-8606 Fix 2FA bypass via RestAPI
- CVE-2022-46836 PHP code injection in watolib
- CVE-2025-32919 Privilege Escalation in Windows License plugin for Checkmk Windows Agent
- CVE-2024-28827 Privilege escalation in Windows agent
Sources
Also known as GHSA-xxw2-9c45-r2hr, UBUNTU-CVE-2026-2859.