{"id":"CVE-2026-2859","aliases":["EUVD-2026-11784","GHSA-xxw2-9c45-r2hr","UBUNTU-CVE-2026-2859"],"status":"published","title":"Unauthenticated Host Enumeration via Observable Response Discrepancy on Deploy Agent Endpoint","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.","severity":{"version":"4.0","score":6.3,"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","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00221,"percentile":0.12746,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-204"],"published":"2026-03-13T09:40:43Z","modified":"2026-10-28T02:30:41Z","affected":[{"source":"osv","ecosystem":"Ubuntu:Pro:16.04:LTS","package":"check-mk","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.2.6p5-1","1.2.6p12-1","1.2.6p12-1ubuntu0.16.04.1","1.2.6p12-1ubuntu0.16.04.1+esm1"]},{"source":"osv","ecosystem":"Ubuntu:18.04:LTS","package":"check-mk","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.2.8p16-1ubuntu0.1","1.2.8p16-1ubuntu0.2"]}],"products":[{"vendor":"checkmk","product":"checkmk"},{"vendor":"checkmk gmbh","product":"checkmk"}],"references":[{"url":"https://checkmk.com/werk/18994","tags":["Vendor Advisory","web","report"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-2859","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-xxw2-9c45-r2hr"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/2xxx/CVE-2026-2859.json","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-2859","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-2859","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-2859","title":"Unauthenticated Host Enumeration via Observable Response Discrepancy on Deploy Agent Endpoint","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 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Checkmk versions 2.4.0 before 2.4.0p23, 2.3.0 before 2.3.0p43,...","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.","status":"published","published":"2026-03-13T21:31:46Z","modified":"2026-03-18T15:30:43Z","cvss":[{"version":"3.1","score":4.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N","level":"medium"},{"version":"4.0","score":6.3,"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/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","level":"medium"}],"cwes":["CWE-204"],"updated_at":"2026-11-02T15:06:41.700997Z"}],"nvd":[{"id":"CVE-2026-2859","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.","status":"published","published":"2026-03-13T19:54:34.227Z","modified":"2026-06-17T10:31:54.09Z","cvss":[{"version":"4.0","score":6.3,"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/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","level":"medium","assessor":"secondary"},{"version":"3.1","score":4.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N","level":"medium","assessor":"primary"}],"cwes":["CWE-204"],"updated_at":"2026-11-02T14:12:09.358914Z"}],"osv":[{"id":"CVE-2026-2859","title":"Unauthenticated Host Enumeration via Observable Response Discrepancy on Deploy Agent Endpoint","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.","status":"published","published":"2026-03-13T09:40:43.743Z","modified":"2026-10-28T02:30:41.875018809Z","cvss":[{"version":"4.0","score":6.3,"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","level":"medium"}],"cwes":["CWE-204"],"updated_at":"2026-11-02T15:45:00.530889Z"},{"id":"UBUNTU-CVE-2026-2859","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.","status":"published","published":"2026-03-13T19:54:00Z","modified":"2026-03-20T08:07:22.922784Z","cvss":[{"version":"4.0","score":6.3,"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","level":"medium"},{"version":"3.1","score":4.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N","level":"medium"}],"updated_at":"2026-11-02T16:56:08.726452Z"}]}}