{"schemaVersion":3,"id":"CVE-2026-15576","aliases":["UBUNTU-CVE-2026-15576"],"status":"published","duplicateOf":null,"title":null,"description":"Improper authentication in the agent receiver of Checkmk <2.5.0p10 allows an unauthenticated remote attacker to bypass mutual TLS client certificate verification of relay endpoints by supplying a fixed placeholder identity in the request URL, resulting in limited impact on integrity and availability. Only the Cloud, Ultimate and Ultimate MT editions are affected, as other editions do not expose relay endpoints.","dates":{"published":"2026-08-21T11:10:00.856Z","modified":"2026-08-21T11:53:45.355Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":6.9,"severity":"medium","version":"4.0","versionLabel":"v4.0","source":"CVE.org","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N","computed":false,"selection":"backend-summary"},"metrics":[{"version":"4.0","versionLabel":"v4.0","source":"CVE.org","score":6.9,"severity":"medium","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N","exploitability":null,"impact":null,"computed":false},{"version":"4.0","versionLabel":"v4.0","source":"OSV · Ubuntu","score":6.9,"severity":"medium","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N","exploitability":null,"impact":null,"computed":true},{"version":"4.0","versionLabel":"v4.0","source":"NVD","score":6.9,"severity":"medium","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/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","exploitability":null,"impact":null,"computed":false}]},"epss":{"probability":0.00453,"percentile":0.38273,"severity":"low","asOf":"2026-10-21T00:00:00.000Z","change":{"pp":0.184,"baselineDate":"2026-09-21T00:00:00.000Z","baselineScore":0.00269},"history":[{"date":"2026-09-14T00:00:00.000Z","score":0.00269,"percentile":null},{"date":"2026-09-15T00:00:00.000Z","score":0.00269,"percentile":null},{"date":"2026-09-16T00:00:00.000Z","score":0.00269,"percentile":null},{"date":"2026-09-17T00:00:00.000Z","score":0.00269,"percentile":null},{"date":"2026-09-18T00:00:00.000Z","score":0.00269,"percentile":null},{"date":"2026-09-19T00:00:00.000Z","score":0.00269,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.00269,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.00269,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.00269,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.00269,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-21T00:00:00.000Z","score":0.00453,"percentile":0.38273}],"last30":[{"date":"2026-09-21T00:00:00.000Z","score":0.00269,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.00269,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.00269,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00453,"percentile":null},{"date":"2026-10-21T00:00:00.000Z","score":0.00453,"percentile":0.38273}]},"kev":{"state":"not-listed","entries":[],"listedCount":0,"totalCatalogs":3,"catalogs":[{"source":"cisa","label":"CISA","listed":false,"entry":null},{"source":"enisa","label":"ENISA","listed":false,"entry":null},{"source":"circl","label":"CIRCL","listed":false,"entry":null}]},"ransomware":{"state":"none-recorded","sources":[]},"exploits":[],"exploitCount":0,"weaknesses":[{"id":"CWE-306","name":"Missing Authentication for Critical Function","description":"The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.","type":"weakness","status":"Draft","abstraction":"Base","likelihoodOfExploit":"High","url":"https://cwe.mitre.org/data/definitions/306.html"}],"affected":[{"vendor":"checkmk gmbh","product":"checkmk","name":"Checkmk","label":"checkmk","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"≥ 2.5.0, < 2.5.0p10","noFixRecorded":false,"fixedIn":null}],"versionsText":"≥ 2.5.0, < 2.5.0p10","eol":{"isEol":null,"eolDate":null,"matchMethod":"name_exact","cycle":null,"product":{"name":"checkmk","label":"Checkmk","category":"server-app"}},"hubHref":"/vendor/checkmk_gmbh/checkmk"},{"vendor":"ubuntu","product":"check-mk","name":"check-mk","label":"check-mk","ecosystem":"Ubuntu","cpePart":null,"purl":"pkg:deb/ubuntu/check-mk","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null}],"versionsText":"All versions (No fix recorded)","eol":null,"hubHref":null}],"affectedCount":2,"eol":{"hasEol":false,"count":0},"references":[{"url":"https://checkmk.com/werk/20174","label":"checkmk.com/werk/20174","hostname":"checkmk.com","tags":["Vendor Advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-15576","label":"ubuntu.com/security/CVE-2026-15576","hostname":"ubuntu.com","tags":["REPORT"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-15576","label":"www.cve.org/CVERecord?id=CVE-2026-15576","hostname":"www.cve.org","tags":["REPORT"]}],"lineage":{"upstream":[],"downstream":[],"duplicates":[],"related":[]},"timeline":[{"kind":"published","date":"2026-08-21T11:10:00.856Z","label":"Published","detail":"Vulnerability first disclosed.","source":null},{"kind":"modified","date":"2026-08-21T11:53:45.355Z","label":"Last modified","detail":"Vulnerability information updated.","source":null}],"risk":{"score":28,"level":"medium","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-22T13:49:17.725Z","stale":false,"partial":false}}