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      {
        "names": [
          "Microsoft Threat Intelligence Center (MSTIC), Microsoft Security Response Center (MSRC), and Office Product Group Security Team"
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      },
      {
        "names": [
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    "aggregate_severity": {
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      "text": "Important"
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    "distribution": {
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      "tlp": {
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    "notes": [
      {
        "category": "general",
        "text": "To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle",
        "title": "Additional Resources"
      },
      {
        "category": "legal_disclaimer",
        "text": "The information provided in the Microsoft Knowledge Base is provided \\\"as is\\\" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.",
        "title": "Disclaimer"
      },
      {
        "category": "general",
        "text": "Required. The vulnerability documented by this CVE requires customer action to resolve.",
        "title": "Customer Action"
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      "name": "Microsoft Security Response Center",
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        "category": "self",
        "summary": "CVE-2026-21509 Microsoft Office Security Feature Bypass Vulnerability - HTML",
        "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21509"
      },
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        "category": "self",
        "summary": "CVE-2026-21509 Microsoft Office Security Feature Bypass Vulnerability - CSAF",
        "url": "https://msrc.microsoft.com/csaf/advisories/2026/msrc_cve-2026-21509.json"
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        "summary": "Microsoft Exploitability Index",
        "url": "https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1"
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        "summary": "Microsoft Support Lifecycle",
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      },
      {
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        "summary": "Common Vulnerability Scoring System",
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    "title": "Microsoft Office Security Feature Bypass Vulnerability",
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      "generator": {
        "date": "2026-01-29T22:43:22.509Z",
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          "date": "2026-01-26T08:00:00.000Z",
          "legacy_version": "1",
          "number": "1",
          "summary": "Information published."
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        {
          "date": "2026-01-26T08:00:00.000Z",
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          "summary": "Corrected CVSS score. This is an informational change only."
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          "date": "2026-01-26T08:00:00.000Z",
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          "number": "3",
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          "date": "2026-01-26T08:00:00.000Z",
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          "number": "4",
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  "id": "GHSA-ch84-h92g-mw93",
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    "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 ZeroDay kwetsbaarheid verholpen in Microsoft Office.",
        "title": "Feiten"
      },
      {
        "category": "description",
        "text": "De kwetsbaarheid bevindt zich in de wijze waarop Microsoft Office omgaat met onbetrouwbare invoer, wat aanvallers in staat stelt om beveiligingsfuncties lokaal te omzeilen. Dit kan de integriteit van beveiligingsbeslissingen die door de software worden genomen, be\u00efnvloeden. De afhankelijkheid van onbetrouwbare invoer cre\u00ebert een pad voor potenti\u00eble exploitatie, wat kan leiden tot ongeautoriseerde toegang of acties binnen de getroffen systemen.\n\nVoor succesvol misbruik moet de kwaadwillende lokale toegang tot het kwetsbare systeem hebben. Dit kan ook mogelijk worden verwezenlijkt door het slachtoffer te misleiden een malafide document te openen.\n\nMicrosoft geeft aan op de hoogte te zijn dat exploitcode gedeeld wordt. De exploitcode is (nog) niet publiek beschikbaar. Het Amerikaanse CISA heeft de kwetsbaarheid op de Known Exploited Vulnerabilities-lijst geplaatst, wat inhoudt dat misbruik van de kwetsbaarheid is bevestigd bij een Amerikaanse Federale overheids-organisatie.",
        "title": "Interpretaties"
      },
      {
        "category": "description",
        "text": "Microsoft heeft updates uitgebracht om de kwetsbaarheid te verhelpen voor Office 2021. Voor Office 2016 en 2019 zijn (nog) geen updates beschikbaar, maar deze worden zeer spoedig verwacht. Wel zijn er mitigerende maatregelen beschikbaar om het risico van misbruik zoveel mogelijk te beperken. Zie bijgevoegde referenties voor meer informatie.",
        "title": "Oplossingen"
      },
      {
        "category": "general",
        "text": "medium",
        "title": "Kans"
      },
      {
        "category": "general",
        "text": "high",
        "title": "Schade"
      },
      {
        "category": "general",
        "text": "Reliance on Untrusted Inputs in a Security Decision",
        "title": "CWE-807"
      }
    ],
    "publisher": {
      "category": "coordinator",
      "contact_details": "cert@ncsc.nl",
      "name": "Nationaal Cyber Security Centrum",
      "namespace": "https://www.ncsc.nl/"
    },
    "references": [
      {
        "category": "external",
        "summary": "Reference",
        "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21509"
      }
    ],
    "title": "ZeroDay kwetsbaarheid verholpen in Microsoft Office",
    "tracking": {
      "current_release_date": "2026-01-27T07:27:52.867415Z",
      "generator": {
        "date": "2025-08-04T16:30:00Z",
        "engine": {
          "name": "V.A.",
          "version": "1.3"
        }
      },
      "id": "NCSC-2026-0039",
      "initial_release_date": "2026-01-27T07:27:52.867415Z",
      "revision_history": [
        {
          "date": "2026-01-27T07:27:52.867415Z",
          "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 365 Apps for Enterprise"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "vers:unknown/*",
                "product": {
                  "name": "vers:unknown/*",
                  "product_id": "CSAFPID-2"
                }
              }
            ],
            "category": "product_name",
            "name": "Microsoft 365 Apps for Enterprise for 32-bit Systems"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "vers:unknown/*",
                "product": {
                  "name": "vers:unknown/*",
                  "product_id": "CSAFPID-3"
                }
              }
            ],
            "category": "product_name",
            "name": "Microsoft 365 Apps for Enterprise for 64-bit Systems"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "vers:unknown/*",
                "product": {
                  "name": "vers:unknown/*",
                  "product_id": "CSAFPID-4"
                }
              }
            ],
            "category": "product_name",
            "name": "Microsoft Office 2016"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "vers:unknown/*",
                "product": {
                  "name": "vers:unknown/*",
                  "product_id": "CSAFPID-5"
                }
              }
            ],
            "category": "product_name",
            "name": "Microsoft Office 2016 (32-bit edition)"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "vers:unknown/*",
                "product": {
                  "name": "vers:unknown/*",
                  "product_id": "CSAFPID-6"
                }
              }
            ],
            "category": "product_name",
            "name": "Microsoft Office 2016 (64-bit edition)"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "vers:unknown/*",
                "product": {
                  "name": "vers:unknown/*",
                  "product_id": "CSAFPID-7"
                }
              }
            ],
            "category": "product_name",
            "name": "Microsoft Office 2019"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "vers:unknown/*",
                "product": {
                  "name": "vers:unknown/*",
                  "product_id": "CSAFPID-8"
                }
              }
            ],
            "category": "product_name",
            "name": "Microsoft Office 2019 for 32-bit editions"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "vers:unknown/*",
                "product": {
                  "name": "vers:unknown/*",
                  "product_id": "CSAFPID-9"
                }
              }
            ],
            "category": "product_name",
            "name": "Microsoft Office 2019 for 64-bit editions"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "vers:unknown/*",
                "product": {
                  "name": "vers:unknown/*",
                  "product_id": "CSAFPID-10"
                }
              }
            ],
            "category": "product_name",
            "name": "Microsoft Office LTSC 2021"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "vers:unknown/*",
                "product": {
                  "name": "vers:unknown/*",
                  "product_id": "CSAFPID-11"
                }
              }
            ],
            "category": "product_name",
            "name": "Microsoft Office LTSC 2021 for 32-bit editions"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "vers:unknown/*",
                "product": {
                  "name": "vers:unknown/*",
                  "product_id": "CSAFPID-12"
                }
              }
            ],
            "category": "product_name",
            "name": "Microsoft Office LTSC 2021 for 64-bit editions"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "vers:unknown/*",
                "product": {
                  "name": "vers:unknown/*",
                  "product_id": "CSAFPID-13"
                }
              }
            ],
            "category": "product_name",
            "name": "Microsoft Office LTSC 2024"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "vers:unknown/*",
                "product": {
                  "name": "vers:unknown/*",
                  "product_id": "CSAFPID-14"
                }
              }
            ],
            "category": "product_name",
            "name": "Microsoft Office LTSC 2024 for 32-bit editions"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "vers:unknown/*",
                "product": {
                  "name": "vers:unknown/*",
                  "product_id": "CSAFPID-15"
                }
              }
            ],
            "category": "product_name",
            "name": "Microsoft Office LTSC 2024 for 64-bit editions"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "vers:unknown/*",
                "product": {
                  "name": "vers:unknown/*",
                  "product_id": "CSAFPID-16"
                }
              }
            ],
            "category": "product_name",
            "name": "Office"
          }
        ],
        "category": "vendor",
        "name": "Microsoft"
      }
    ]
  },
  "vulnerabilities": [
    {
      "cve": "CVE-2026-21509",
      "cwe": {
        "id": "CWE-807",
        "name": "Reliance on Untrusted Inputs in a Security Decision"
      },
      "notes": [
        {
          "category": "other",
          "text": "Reliance on Untrusted Inputs in a Security Decision",
          "title": "CWE-807"
        },
        {
          "category": "description",
          "text": "Microsoft Office has a vulnerability that allows unauthorized attackers to locally bypass security features by exploiting untrusted inputs in security decisions.",
          "title": "Summary"
        }
      ],
      "product_status": {
        "known_affected": [
          "CSAFPID-1",
          "CSAFPID-2",
          "CSAFPID-3",
          "CSAFPID-4",
          "CSAFPID-5",
          "CSAFPID-6",
          "CSAFPID-7",
          "CSAFPID-8",
          "CSAFPID-9",
          "CSAFPID-10",
          "CSAFPID-11",
          "CSAFPID-12",
          "CSAFPID-13",
          "CSAFPID-14",
          "CSAFPID-15",
          "CSAFPID-16"
        ]
      },
      "references": [
        {
          "category": "self",
          "summary": "CVE-2026-21509 | NCSC-NL Website",
          "url": "https://vulnerabilities.ncsc.nl/csaf/v2/2026/cve-2026-21509.json"
        }
      ],
      "scores": [
        {
          "cvss_v3": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C",
            "version": "3.1"
          },
          "products": [
            "CSAFPID-1",
            "CSAFPID-2",
            "CSAFPID-3",
            "CSAFPID-4",
            "CSAFPID-5",
            "CSAFPID-6",
            "CSAFPID-7",
            "CSAFPID-8",
            "CSAFPID-9",
            "CSAFPID-10",
            "CSAFPID-11",
            "CSAFPID-12",
            "CSAFPID-13",
            "CSAFPID-14",
            "CSAFPID-15",
            "CSAFPID-16"
          ]
        }
      ],
      "title": "CVE-2026-21509"
    }
  ]
}

{
  "$ref": "https://www.cert.ssi.gouv.fr/openapi.json",
  "affected_systems": [
    {
      "description": "Microsoft Office LTSC 2021 pour \u00e9ditions 64 bits",
      "product": {
        "name": "Office",
        "vendor": {
          "name": "Microsoft",
          "scada": false
        }
      }
    },
    {
      "description": "Microsoft Office LTSC 2021 pour \u00e9ditions 32 bits",
      "product": {
        "name": "Office",
        "vendor": {
          "name": "Microsoft",
          "scada": false
        }
      }
    },
    {
      "description": "Microsoft Office 2019 pour \u00e9ditions 32 bits",
      "product": {
        "name": "Office",
        "vendor": {
          "name": "Microsoft",
          "scada": false
        }
      }
    },
    {
      "description": "Microsoft 365 Apps pour Enterprise pour syst\u00e8mes 64 bits",
      "product": {
        "name": "Office",
        "vendor": {
          "name": "Microsoft",
          "scada": false
        }
      }
    },
    {
      "description": "Microsoft Office 2019 pour \u00e9ditions 64 bits",
      "product": {
        "name": "Office",
        "vendor": {
          "name": "Microsoft",
          "scada": false
        }
      }
    },
    {
      "description": "Microsoft Office LTSC 2024 pour \u00e9ditions 64 bits",
      "product": {
        "name": "Office",
        "vendor": {
          "name": "Microsoft",
          "scada": false
        }
      }
    },
    {
      "description": "Microsoft Office 2016 (\u00e9dition 64 bits)",
      "product": {
        "name": "Office",
        "vendor": {
          "name": "Microsoft",
          "scada": false
        }
      }
    },
    {
      "description": "Microsoft Office 2016 (\u00e9dition 32 bits)",
      "product": {
        "name": "Office",
        "vendor": {
          "name": "Microsoft",
          "scada": false
        }
      }
    },
    {
      "description": "Microsoft Office LTSC 2024 pour \u00e9ditions 32 bits",
      "product": {
        "name": "Office",
        "vendor": {
          "name": "Microsoft",
          "scada": false
        }
      }
    },
    {
      "description": "Microsoft 365 Apps pour Enterprise pour syst\u00e8mes 32 bits",
      "product": {
        "name": "Office",
        "vendor": {
          "name": "Microsoft",
          "scada": false
        }
      }
    }
  ],
  "affected_systems_content": "",
  "content": "## Solutions\n\nSe r\u00e9f\u00e9rer au bulletin de s\u00e9curit\u00e9 de l\u0027\u00e9diteur pour l\u0027obtention des correctifs (cf. section Documentation).",
  "cves": [
    {
      "name": "CVE-2026-21509",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-21509"
    }
  ],
  "initial_release_date": "2026-01-27T00:00:00",
  "last_revision_date": "2026-01-27T00:00:00",
  "links": [],
  "reference": "CERTFR-2026-AVI-0089",
  "revisions": [
    {
      "description": "Version initiale",
      "revision_date": "2026-01-27T00:00:00.000000"
    }
  ],
  "risks": [
    {
      "description": "Contournement de la politique de s\u00e9curit\u00e9"
    }
  ],
  "summary": "Une vuln\u00e9rabilit\u00e9 a \u00e9t\u00e9 d\u00e9couverte dans Microsoft Office. Elle permet \u00e0 un attaquant de provoquer un contournement de la politique de s\u00e9curit\u00e9.\n\nMicrosoft indique que la vuln\u00e9rabilit\u00e9 CVE-2026-21509 est activement exploit\u00e9e.",
  "title": "Vuln\u00e9rabilit\u00e9 dans Microsoft Office",
  "vendor_advisories": [
    {
      "published_at": "2026-01-26",
      "title": "Bulletin de s\u00e9curit\u00e9 Microsoft Office CVE-2026-21509",
      "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21509"
    }
  ]
}