{
  "document": {
    "category": "csaf_security_advisory",
    "csaf_version": "2.0",
    "distribution": {
      "tlp": {
        "label": "WHITE"
      }
    },
    "lang": "nl",
    "notes": [
      {
        "category": "legal_disclaimer",
        "text": "The Netherlands Cyber Security Center (henceforth: NCSC-NL) maintains this page to enhance access to its information and security advisories. The use of this security advisory is subject to the following terms and conditions:\n\n    NCSC-NL makes every reasonable effort to ensure that the content of this page is kept up to date, and that it is accurate and complete. Nevertheless, NCSC-NL cannot entirely rule out the possibility of errors, and therefore cannot give any warranty in respect of its completeness, accuracy or continuous keeping up-to-date. The information contained in this security advisory is intended solely for the purpose of providing general information to professional users. No rights can be derived from the information provided therein.\n\n    NCSC-NL and the Kingdom of the Netherlands assume no legal liability or responsibility for any damage resulting from either the use or inability of use of this security advisory. This includes damage resulting from the inaccuracy of incompleteness of the information contained in the advisory.\n    This security advisory is subject to Dutch law. All disputes related to or arising from the use of this advisory will be submitted to the competent court in The Hague. This choice of means also applies to the court in summary proceedings."
      },
      {
        "category": "description",
        "text": "Microsoft heeft een kwetsbaarheid verholpen in Exchange server.",
        "title": "Feiten"
      },
      {
        "category": "description",
        "text": "Een kwaadwillende kan zich, zonder voorafgaande authenticatie, voordoen als andere gebruiker en op die manier toegang krijgen tot gevoelige gegevens in de context van het slachtoffer.",
        "title": "Interpretaties"
      },
      {
        "category": "description",
        "text": "Microsoft heeft updates beschikbaar gesteld waarmee de beschreven kwetsbaarheid wordt verholpen. We raden u aan om deze updates te installeren. Meer informatie over de kwetsbaarheid, de installatie van de updates en eventuele work-arounds vindt u op:\n\nhttps://portal.msrc.microsoft.com/en-us/security-guidance",
        "title": "Oplossingen"
      },
      {
        "category": "general",
        "text": "medium",
        "title": "Kans"
      },
      {
        "category": "general",
        "text": "high",
        "title": "Schade"
      },
      {
        "category": "general",
        "text": "Insufficient Verification of Data Authenticity",
        "title": "CWE-345"
      },
      {
        "category": "general",
        "text": "User Interface (UI) Misrepresentation of Critical Information",
        "title": "CWE-451"
      },
      {
        "category": "general",
        "text": "Improper Validation of Syntactic Correctness of Input",
        "title": "CWE-1286"
      }
    ],
    "publisher": {
      "category": "coordinator",
      "contact_details": "cert@ncsc.nl",
      "name": "Nationaal Cyber Security Centrum",
      "namespace": "https://www.ncsc.nl/"
    },
    "title": "Kwetsbaarheid verholpen in Microsoft Exchange",
    "tracking": {
      "current_release_date": "2026-02-10T19:04:51.366294Z",
      "generator": {
        "date": "2025-08-04T16:30:00Z",
        "engine": {
          "name": "V.A.",
          "version": "1.3"
        }
      },
      "id": "NCSC-2026-0054",
      "initial_release_date": "2026-02-10T19:04:51.366294Z",
      "revision_history": [
        {
          "date": "2026-02-10T19:04:51.366294Z",
          "number": "1.0.0",
          "summary": "Initiele versie"
        }
      ],
      "status": "final",
      "version": "1.0.0"
    }
  },
  "product_tree": {
    "branches": [
      {
        "branches": [
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "vers:unknown/*",
                "product": {
                  "name": "vers:unknown/*",
                  "product_id": "CSAFPID-1"
                }
              }
            ],
            "category": "product_name",
            "name": "Microsoft Exchange Server 2016 Cumulative Update 23"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "vers:unknown/*",
                "product": {
                  "name": "vers:unknown/*",
                  "product_id": "CSAFPID-2"
                }
              }
            ],
            "category": "product_name",
            "name": "Microsoft Exchange Server 2019 Cumulative Update 14"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "vers:unknown/*",
                "product": {
                  "name": "vers:unknown/*",
                  "product_id": "CSAFPID-3"
                }
              }
            ],
            "category": "product_name",
            "name": "Microsoft Exchange Server 2019 Cumulative Update 15"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "vers:unknown/*",
                "product": {
                  "name": "vers:unknown/*",
                  "product_id": "CSAFPID-4"
                }
              }
            ],
            "category": "product_name",
            "name": "Microsoft Exchange Server Subscription Edition RTM"
          }
        ],
        "category": "vendor",
        "name": "Microsoft"
      }
    ]
  },
  "vulnerabilities": [
    {
      "cve": "CVE-2026-21527",
      "cwe": {
        "id": "CWE-1286",
        "name": "Improper Validation of Syntactic Correctness of Input"
      },
      "notes": [
        {
          "category": "other",
          "text": "Improper Validation of Syntactic Correctness of Input",
          "title": "CWE-1286"
        },
        {
          "category": "other",
          "text": "Insufficient Verification of Data Authenticity",
          "title": "CWE-345"
        },
        {
          "category": "other",
          "text": "User Interface (UI) Misrepresentation of Critical Information",
          "title": "CWE-451"
        },
        {
          "category": "description",
          "text": "A vulnerability in Microsoft Exchange Server allows unauthorized attackers to spoof information over a network due to user interface misrepresentation.",
          "title": "Summary"
        }
      ],
      "product_status": {
        "known_affected": [
          "CSAFPID-1",
          "CSAFPID-2",
          "CSAFPID-3",
          "CSAFPID-4"
        ]
      },
      "references": [
        {
          "category": "self",
          "summary": "CVE-2026-21527 | NCSC-NL Website",
          "url": "https://vulnerabilities.ncsc.nl/csaf/v2/2026/cve-2026-21527.json"
        }
      ],
      "scores": [
        {
          "cvss_v3": {
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N/E:U/RL:O/RC:C",
            "version": "3.1"
          },
          "products": [
            "CSAFPID-1",
            "CSAFPID-2",
            "CSAFPID-3",
            "CSAFPID-4"
          ]
        }
      ],
      "title": "CVE-2026-21527"
    }
  ]
}