{
  "cveId": "CVE-2021-42321",
  "url": "https://patchblox.com/security/cve/CVE-2021-42321",
  "summary": "CVE-2021-42321 is fixed in 4 products on 1 platform, first by KB5007409, released November 9, 2021. It is being exploited: CISA added it to the Known Exploited Vulnerabilities catalog on November 17, 2021, with known ransomware use. Patch Radar priority: Patch now.",
  "title": "Microsoft Exchange Server Remote Code Execution Vulnerability",
  "description": "",
  "published": "2021-11-17T14:00:00Z",
  "severity": "Important",
  "cvss": 8.8,
  "epss": 0.91737,
  "epssPercentile": 0.99816,
  "priority": "Patch now",
  "priorityTier": 1,
  "exploited": true,
  "vendorExploited": true,
  "disclosed": false,
  "exploitabilityAssessment": "Exploitation Detected",
  "kev": {
    "added": "2021-11-17T00:00:00Z",
    "due": "2021-12-01T00:00:00Z",
    "ransomware": true,
    "requiredAction": "Apply updates per vendor instructions."
  },
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-42321",
  "fixes": [
    {
      "platform": "microsoft",
      "product": "Microsoft Exchange Server 2016 Cumulative Update 21",
      "fixedVersion": "",
      "fix": "KB5007409",
      "url": "https://patchblox.com/security/fix/microsoft/kb5007409",
      "released": "2021-11-09T14:00:00Z"
    },
    {
      "platform": "microsoft",
      "product": "Microsoft Exchange Server 2016 Cumulative Update 22",
      "fixedVersion": "",
      "fix": "KB5007409",
      "url": "https://patchblox.com/security/fix/microsoft/kb5007409",
      "released": "2021-11-09T14:00:00Z"
    },
    {
      "platform": "microsoft",
      "product": "Microsoft Exchange Server 2019 Cumulative Update 10",
      "fixedVersion": "",
      "fix": "KB5007409",
      "url": "https://patchblox.com/security/fix/microsoft/kb5007409",
      "released": "2021-11-09T14:00:00Z"
    },
    {
      "platform": "microsoft",
      "product": "Microsoft Exchange Server 2019 Cumulative Update 11",
      "fixedVersion": "",
      "fix": "KB5007409",
      "url": "https://patchblox.com/security/fix/microsoft/kb5007409",
      "released": "2021-11-09T14:00:00Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-09T13:31:49Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}