{"schemaVersion":3,"id":"CVE-2026-55996","aliases":[],"status":"published","duplicateOf":null,"title":null,"description":"A denial-of-service vulnerability was identified in multiple TLS listeners in Rancher. Both the cattle-cluster-agent component running in downstream clusters and the Rancher server itself use the dynamiclistener library to serve TLS traffic. Without an effective CN filter configured, dynamiclistener automatically appended to each serving certificate any hostname presented via Server Name Indication (SNI) in incoming TLS requests.\n\n\n\nAn unauthenticated attacker with network access within the affected cluster could send a large number of TLS requests with distinct hostnames, causing the serving certificate to accumulate an unbounded number of Subject Alternative Names (SANs). Eventually, the certificate grows large enough that TLS handshakes fail with an excessive message size error, causing a denial of service on the affected listeners.","dates":{"published":"2026-08-05T07:46:43.831Z","modified":"2026-08-05T19:05:26.627Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":4.3,"severity":"medium","version":"3.1","versionLabel":"v3.1","source":"CVE.org","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L","computed":false,"selection":"backend-summary"},"metrics":[{"version":"3.1","versionLabel":"v3.1","source":"CVE.org","score":4.3,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L","exploitability":null,"impact":null,"computed":false},{"version":"3.1","versionLabel":"v3.1","source":"NVD","score":4.3,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L","exploitability":null,"impact":null,"computed":false}]},"epss":{"probability":0.00245,"percentile":0.14686,"severity":"low","asOf":"2026-10-19T00:00:00.000Z","change":{"pp":0.09499999999999999,"baselineDate":"2026-09-19T00:00:00.000Z","baselineScore":0.0015},"history":[{"date":"2026-09-14T00:00:00.000Z","score":0.0015,"percentile":null},{"date":"2026-09-15T00:00:00.000Z","score":0.0015,"percentile":null},{"date":"2026-09-16T00:00:00.000Z","score":0.0015,"percentile":null},{"date":"2026-09-17T00:00:00.000Z","score":0.0015,"percentile":null},{"date":"2026-09-18T00:00:00.000Z","score":0.0015,"percentile":null},{"date":"2026-09-19T00:00:00.000Z","score":0.0015,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.0015,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.0015,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.0015,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.0015,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00245,"percentile":0.14686}],"last30":[{"date":"2026-09-19T00:00:00.000Z","score":0.0015,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.0015,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.0015,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.0015,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.0015,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00245,"percentile":null},{"date":"2026-10-10T00:00:00.000Z"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of Resources Without Limits or Throttling","description":"The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.","type":"weakness","status":"Incomplete","abstraction":"Base","likelihoodOfExploit":"High","url":"https://cwe.mitre.org/data/definitions/770.html"}],"affected":[{"vendor":"suse","product":"rancher","name":"rancher","label":"rancher","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"≥ 2.11.0, < 2.11.16","noFixRecorded":false,"fixedIn":null},{"text":"≥ 2.12.0, < 2.12.12","noFixRecorded":false,"fixedIn":null},{"text":"≥ 2.13.0, < 2.13.8","noFixRecorded":false,"fixedIn":null},{"text":"≥ 2.14.0, < 2.14.4","noFixRecorded":false,"fixedIn":null}],"versionsText":"≥ 2.11.0, < 2.11.16 | ≥ 2.12.0, < 2.12.12 | ≥ 2.13.0, < 2.13.8 | ≥ 2.14.0, < 2.14.4","eol":{"isEol":null,"eolDate":null,"matchMethod":"cpe","cycle":null,"product":{"name":"rancher","label":"Rancher","category":"server-app"}},"hubHref":"/vendor/suse/rancher"}],"affectedCount":1,"eol":{"hasEol":false,"count":0},"references":[{"url":"https://github.com/rancher/rancher/security/advisories/GHSA-9jxv-832x-45q9","label":"github.com/rancher/rancher/security/advisories/GHSA-9jxv-832x-45q9","hostname":"github.com","tags":[]},{"url":"https://bugzilla.suse.com/show_bug.cgi?id=CVE-2026-55996","label":"bugzilla.suse.com/show_bug.cgi?id=CVE-2026-55996","hostname":"bugzilla.suse.com","tags":[]}],"lineage":{"upstream":[],"downstream":[],"duplicates":[],"related":[]},"timeline":[{"kind":"published","date":"2026-08-05T07:46:43.831Z","label":"Published","detail":"Vulnerability first disclosed.","source":null},{"kind":"modified","date":"2026-08-05T19:05:26.627Z","label":"Last modified","detail":"Vulnerability information updated.","source":null}],"risk":{"score":17,"level":"low","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-20T05:36:40.786Z","stale":false,"partial":false}}