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CVE-2021-26854

Status: ModifiedHigh (7.2)—

Microsoft Exchange Server Remote Code Execution Vulnerability

CVSS

Exploitation probability (EPSS)

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Affected technologies (1)

Microsoft — Exchange Server

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2021-26854",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 6.5,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:L/Au:S/C:P/I:P/A:P",
          "authentication": "SINGLE",
          "integrityImpact": "PARTIAL",
          "accessComplexity": "LOW",
          "availabilityImpact": "PARTIAL",
          "confidentialityImpact": "PARTIAL"
        },
        "acInsufInfo": false,
        "impactScore": 6.4,
        "baseSeverity": "MEDIUM",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 8,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "secure@microsoft.com",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 6.6,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "HIGH",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "HIGH",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 0.7
      },
      {
        "type": "Secondary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.2,
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "HIGH",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 1.2
      }
    ]
  },
  "affected": [
    {
      "source": "secure@microsoft.com",
      "affectedData": [
        {
          "vendor": "Microsoft",
          "product": "Microsoft Exchange Server 2013 Cumulative Update 23",
          "versions": [
            {
              "status": "affected",
              "version": "15.00.0",
              "lessThan": "15.00.1497.012",
              "versionType": "custom"
            }
          ],
          "platforms": [
            "x64-based Systems"
          ]
        },
        {
          "vendor": "Microsoft",
          "product": "Microsoft Exchange Server 2016 Cumulative Update 18",
          "versions": [
            {
              "status": "affected",
              "version": "15.01.0",
              "lessThan": "15.01.2106.013",
              "versionType": "custom"
            }
          ],
          "platforms": [
            "x64-based Systems"
          ]
        },
        {
          "vendor": "Microsoft",
          "product": "Microsoft Exchange Server 2016 Cumulative Update 19",
          "versions": [
            {
              "status": "affected",
              "version": "15.01.0",
              "lessThan": "15.01.2176.009",
              "versionType": "custom"
            }
          ],
          "platforms": [
            "x64-based Systems"
          ]
        },
        {
          "vendor": "Microsoft",
          "product": "Microsoft Exchange Server 2019 Cumulative Update 7",
          "versions": [
            {
              "status": "affected",
              "version": "15.02.0",
              "lessThan": "15.02.0721.013",
              "versionType": "custom"
            }
          ],
          "platforms": [
            "x64-based Systems"
          ]
        },
        {
          "vendor": "Microsoft",
          "product": "Microsoft Exchange Server 2019 Cumulative Update 8",
          "versions": [
            {
              "status": "affected",
              "version": "15.02.0",
              "lessThan": "15.02.0792.010",
              "versionType": "custom"
            }
          ],
          "platforms": [
            "x64-based Systems"
          ]
        }
      ]
    }
  ],
  "published": "2021-03-03T00:15:12.040",
  "references": [
    {
      "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26854",
      "source": "secure@microsoft.com"
    },
    {
      "url": "https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26854",
      "tags": [
        "Patch",
        "Vendor Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "NVD-CWE-noinfo"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Microsoft Exchange Server Remote Code Execution Vulnerability"
    },
    {
      "lang": "es",
      "value": "Una Vulnerabilidad de Ejecución de código remota de Microsoft Exchange Server. Este ID de CVE es diferente de CVE-2021-26412, CVE-2021-26855, CVE-2021-26857, CVE-2021-26858, CVE-2021-27065, CVE-2021-27078"
    }
  ],
  "lastModified": "2026-08-19T17:17:37.907",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_23:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "DA166F2A-D83B-4D50-AD0B-668D813E0585"
            },
            {
              "criteria": "cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_18:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "29805EC7-6403-44B9-91EC-109C087E98EB"
            },
            {
              "criteria": "cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_19:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "28FCA0E8-7D27-4746-9731-91B834CA3E64"
            },
            {
              "criteria": "cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_7:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "36CE5C6D-9A04-41F5-AE7C-265779833649"
            },
            {
              "criteria": "cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_8:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "44ECF39A-1DE1-4870-A494-06A53494338D"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "secure@microsoft.com"
}