{
  "containers": {
    "cna": {
      "affected": [
        {
          "product": "Microsoft Exchange Online",
          "vendor": "Microsoft",
          "versions": [
            {
              "status": "affected",
              "version": "-"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:a:microsoft:exchange_online:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "-",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "datePublic": "2026-07-23T14:00:00.000Z",
      "descriptions": [
        {
          "lang": "en-US",
          "value": "Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform tampering over a network."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 10,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en-US",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-287",
              "description": "CWE-287: Improper Authentication",
              "lang": "en-US",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-24T19:36:26.877Z",
        "orgId": "f38d906d-7342-40ea-92c1-6c4a2c6478c8",
        "shortName": "microsoft"
      },
      "references": [
        {
          "name": "Microsoft Exchange Online Tampering Vulnerability",
          "tags": [
            "vendor-advisory",
            "patch"
          ],
          "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56191"
        }
      ],
      "tags": [
        "exclusively-hosted-service"
      ],
      "title": "Microsoft Exchange Online Tampering Vulnerability"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "f38d906d-7342-40ea-92c1-6c4a2c6478c8",
    "assignerShortName": "microsoft",
    "cveId": "CVE-2026-56191",
    "datePublished": "2026-07-24T00:01:12.361Z",
    "dateReserved": "2026-06-19T13:54:04.006Z",
    "dateUpdated": "2026-07-24T19:36:26.877Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-56191",
      "date": "2026-07-24",
      "epss": "0.00681",
      "percentile": "0.4865"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-56191\",\"sourceIdentifier\":\"secure@microsoft.com\",\"published\":\"2026-07-24T01:17:36.417\",\"lastModified\":\"2026-07-24T01:17:36.417\",\"vulnStatus\":\"Received\",\"cveTags\":[{\"sourceIdentifier\":\"secure@microsoft.com\",\"tags\":[\"exclusively-hosted-service\"]}],\"descriptions\":[{\"lang\":\"en\",\"value\":\"Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform tampering over a network.\"}],\"affected\":[{\"source\":\"secure@microsoft.com\",\"affectedData\":[{\"vendor\":\"Microsoft\",\"product\":\"Microsoft Exchange Online\",\"versions\":[{\"version\":\"-\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"secure@microsoft.com\",\"type\":\"Primary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H\",\"baseScore\":10.0,\"baseSeverity\":\"CRITICAL\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"CHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":3.9,\"impactScore\":6.0}]},\"weaknesses\":[{\"source\":\"secure@microsoft.com\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-287\"}]}],\"references\":[{\"url\":\"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56191\",\"source\":\"secure@microsoft.com\"}]}}"
  }
}