{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Integer underflow (wrap or wraparound) in Microsoft Office Excel allows an unauthorized attacker to execute code locally."
    }
  ],
  "id": "CVE-2026-44820",
  "lastModified": "2026-06-09T19:32:51.440",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 7.8,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "REQUIRED",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.9,
        "source": "secure@microsoft.com",
        "type": "Primary"
      }
    ]
  },
  "published": "2026-06-09T17:17:18.313",
  "references": [
    {
      "source": "secure@microsoft.com",
      "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-44820"
    }
  ],
  "sourceIdentifier": "secure@microsoft.com",
  "vulnStatus": "Awaiting Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-125"
        }
      ],
      "source": "secure@microsoft.com",
      "type": "Primary"
    }
  ]
}

{
  "affected": [],
  "aliases": [
    "CVE-2026-44820"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-125"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-06-09T17:17:18Z",
    "severity": "HIGH"
  },
  "details": "Integer underflow (wrap or wraparound) in Microsoft Office Excel allows an unauthorized attacker to execute code locally.",
  "id": "GHSA-837c-8j3p-37gw",
  "modified": "2026-06-09T18:30:48Z",
  "published": "2026-06-09T18:30:47Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44820"
    },
    {
      "type": "WEB",
      "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-44820"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

{
  "document": {
    "acknowledgments": [
      {
        "names": [
          "\u003ca href=\"https://x.com/dnpushme\"\u003ef4 \u0026amp; Zhiniang Peng with HUST\u003c/a\u003e"
        ]
      }
    ],
    "aggregate_severity": {
      "namespace": "https://www.microsoft.com/en-us/msrc/security-update-severity-rating-system",
      "text": "Important"
    },
    "category": "csaf_security_advisory",
    "csaf_version": "2.0",
    "distribution": {
      "text": "Public",
      "tlp": {
        "label": "WHITE",
        "url": "https://www.first.org/tlp/"
      }
    },
    "lang": "en-US",
    "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"
      }
    ],
    "publisher": {
      "category": "vendor",
      "contact_details": "secure@microsoft.com",
      "name": "Microsoft Security Response Center",
      "namespace": "https://msrc.microsoft.com"
    },
    "references": [
      {
        "category": "self",
        "summary": "CVE-2026-44820 Microsoft Excel Remote Code Execution Vulnerability - HTML",
        "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-44820"
      },
      {
        "category": "self",
        "summary": "CVE-2026-44820 Microsoft Excel Remote Code Execution Vulnerability - CSAF",
        "url": "https://msrc.microsoft.com/csaf/advisories/2026/msrc_cve-2026-44820.json"
      },
      {
        "category": "external",
        "summary": "Microsoft Exploitability Index",
        "url": "https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1"
      },
      {
        "category": "external",
        "summary": "Microsoft Support Lifecycle",
        "url": "https://support.microsoft.com/lifecycle"
      },
      {
        "category": "external",
        "summary": "Common Vulnerability Scoring System",
        "url": "https://www.first.org/cvss"
      }
    ],
    "title": "Microsoft Excel Remote Code Execution Vulnerability",
    "tracking": {
      "current_release_date": "2026-06-09T07:00:00.000Z",
      "generator": {
        "date": "2026-06-09T17:04:14.510Z",
        "engine": {
          "name": "MSRC Generator",
          "version": "1.0"
        }
      },
      "id": "msrc_CVE-2026-44820",
      "initial_release_date": "2026-06-09T07:00:00.000Z",
      "revision_history": [
        {
          "date": "2026-06-09T07:00:00.000Z",
          "legacy_version": "1",
          "number": "1",
          "summary": "Information published."
        }
      ],
      "status": "final",
      "version": "1"
    }
  },
  "product_tree": {
    "branches": [
      {
        "branches": [
          {
            "category": "product_version_range",
            "name": "\u003c16.0.10417.20137",
            "product": {
              "name": "Office Online Server \u003c16.0.10417.20137",
              "product_id": "12"
            }
          },
          {
            "category": "product_version",
            "name": "16.0.10417.20137",
            "product": {
              "name": "Office Online Server 16.0.10417.20137",
              "product_id": "10836"
            }
          }
        ],
        "category": "product_name",
        "name": "Office Online Server"
      },
      {
        "branches": [
          {
            "category": "product_version_range",
            "name": "\u003chttps://aka.ms/OfficeSecurityReleases",
            "product": {
              "name": "Microsoft Office 2019 for 32-bit editions \u003chttps://aka.ms/OfficeSecurityReleases",
              "product_id": "11"
            }
          },
          {
            "category": "product_version",
            "name": "https://aka.ms/OfficeSecurityReleases",
            "product": {
              "name": "Microsoft Office 2019 for 32-bit editions https://aka.ms/OfficeSecurityReleases",
              "product_id": "11573"
            }
          }
        ],
        "category": "product_name",
        "name": "Microsoft Office 2019 for 32-bit editions"
      },
      {
        "branches": [
          {
            "category": "product_version_range",
            "name": "\u003chttps://aka.ms/OfficeSecurityReleases",
            "product": {
              "name": "Microsoft Office 2019 for 64-bit editions \u003chttps://aka.ms/OfficeSecurityReleases",
              "product_id": "10"
            }
          },
          {
            "category": "product_version",
            "name": "https://aka.ms/OfficeSecurityReleases",
            "product": {
              "name": "Microsoft Office 2019 for 64-bit editions https://aka.ms/OfficeSecurityReleases",
              "product_id": "11574"
            }
          }
        ],
        "category": "product_name",
        "name": "Microsoft Office 2019 for 64-bit editions"
      },
      {
        "branches": [
          {
            "category": "product_version_range",
            "name": "\u003chttps://aka.ms/OfficeSecurityReleases",
            "product": {
              "name": "Microsoft 365 Apps for Enterprise for 32-bit Systems \u003chttps://aka.ms/OfficeSecurityReleases",
              "product_id": "9"
            }
          },
          {
            "category": "product_version",
            "name": "https://aka.ms/OfficeSecurityReleases",
            "product": {
              "name": "Microsoft 365 Apps for Enterprise for 32-bit Systems https://aka.ms/OfficeSecurityReleases",
              "product_id": "11762"
            }
          }
        ],
        "category": "product_name",
        "name": "Microsoft 365 Apps for Enterprise for 32-bit Systems"
      },
      {
        "branches": [
          {
            "category": "product_version_range",
            "name": "\u003chttps://aka.ms/OfficeSecurityReleases",
            "product": {
              "name": "Microsoft 365 Apps for Enterprise for 64-bit Systems \u003chttps://aka.ms/OfficeSecurityReleases",
              "product_id": "8"
            }
          },
          {
            "category": "product_version",
            "name": "https://aka.ms/OfficeSecurityReleases",
            "product": {
              "name": "Microsoft 365 Apps for Enterprise for 64-bit Systems https://aka.ms/OfficeSecurityReleases",
              "product_id": "11763"
            }
          }
        ],
        "category": "product_name",
        "name": "Microsoft 365 Apps for Enterprise for 64-bit Systems"
      },
      {
        "branches": [
          {
            "category": "product_version_range",
            "name": "\u003chttps://aka.ms/OfficeSecurityReleases",
            "product": {
              "name": "Microsoft Office LTSC 2021 for 64-bit editions \u003chttps://aka.ms/OfficeSecurityReleases",
              "product_id": "6"
            }
          },
          {
            "category": "product_version",
            "name": "https://aka.ms/OfficeSecurityReleases",
            "product": {
              "name": "Microsoft Office LTSC 2021 for 64-bit editions https://aka.ms/OfficeSecurityReleases",
              "product_id": "11952"
            }
          }
        ],
        "category": "product_name",
        "name": "Microsoft Office LTSC 2021 for 64-bit editions"
      },
      {
        "branches": [
          {
            "category": "product_version_range",
            "name": "\u003chttps://aka.ms/OfficeSecurityReleases",
            "product": {
              "name": "Microsoft Office LTSC 2021 for 32-bit editions \u003chttps://aka.ms/OfficeSecurityReleases",
              "product_id": "5"
            }
          },
          {
            "category": "product_version",
            "name": "https://aka.ms/OfficeSecurityReleases",
            "product": {
              "name": "Microsoft Office LTSC 2021 for 32-bit editions https://aka.ms/OfficeSecurityReleases",
              "product_id": "11953"
            }
          }
        ],
        "category": "product_name",
        "name": "Microsoft Office LTSC 2021 for 32-bit editions"
      },
      {
        "branches": [
          {
            "category": "product_version_range",
            "name": "\u003chttps://aka.ms/OfficeSecurityReleases",
            "product": {
              "name": "Microsoft Office LTSC 2024 for 32-bit editions \u003chttps://aka.ms/OfficeSecurityReleases",
              "product_id": "4"
            }
          },
          {
            "category": "product_version",
            "name": "https://aka.ms/OfficeSecurityReleases",
            "product": {
              "name": "Microsoft Office LTSC 2024 for 32-bit editions https://aka.ms/OfficeSecurityReleases",
              "product_id": "12420"
            }
          }
        ],
        "category": "product_name",
        "name": "Microsoft Office LTSC 2024 for 32-bit editions"
      },
      {
        "branches": [
          {
            "category": "product_version_range",
            "name": "\u003chttps://aka.ms/OfficeSecurityReleases",
            "product": {
              "name": "Microsoft Office LTSC 2024 for 64-bit editions \u003chttps://aka.ms/OfficeSecurityReleases",
              "product_id": "3"
            }
          },
          {
            "category": "product_version",
            "name": "https://aka.ms/OfficeSecurityReleases",
            "product": {
              "name": "Microsoft Office LTSC 2024 for 64-bit editions https://aka.ms/OfficeSecurityReleases",
              "product_id": "12421"
            }
          }
        ],
        "category": "product_name",
        "name": "Microsoft Office LTSC 2024 for 64-bit editions"
      },
      {
        "branches": [
          {
            "category": "product_version_range",
            "name": "\u003c16.0.5556.1001",
            "product": {
              "name": "Microsoft Excel 2016 (32-bit edition) \u003c16.0.5556.1001",
              "product_id": "14"
            }
          },
          {
            "category": "product_version",
            "name": "16.0.5556.1001",
            "product": {
              "name": "Microsoft Excel 2016 (32-bit edition) 16.0.5556.1001",
              "product_id": "10739"
            }
          }
        ],
        "category": "product_name",
        "name": "Microsoft Excel 2016 (32-bit edition)"
      },
      {
        "branches": [
          {
            "category": "product_version_range",
            "name": "\u003c16.0.5556.1001",
            "product": {
              "name": "Microsoft Excel 2016 (64-bit edition) \u003c16.0.5556.1001",
              "product_id": "13"
            }
          },
          {
            "category": "product_version",
            "name": "16.0.5556.1001",
            "product": {
              "name": "Microsoft Excel 2016 (64-bit edition) 16.0.5556.1001",
              "product_id": "10740"
            }
          }
        ],
        "category": "product_name",
        "name": "Microsoft Excel 2016 (64-bit edition)"
      }
    ]
  },
  "vulnerabilities": [
    {
      "cve": "CVE-2026-44820",
      "cwe": {
        "id": "CWE-125",
        "name": "Out-of-bounds Read"
      },
      "notes": [
        {
          "category": "general",
          "text": "Microsoft",
          "title": "Assigning CNA"
        },
        {
          "category": "faq",
          "text": "The word Remote in the title refers to the location of the attacker. This type of exploit is sometimes referred to as Arbitrary Code Execution (ACE). The attack itself is carried out locally. This means an attacker or victim needs to execute code from the local machine to exploit the vulnerability.",
          "title": "According to the CVSS metric, the attack vector is local (AV:L). Why does the CVE title indicate that this is a remote code execution?"
        },
        {
          "category": "faq",
          "text": "An attacker must send a user a malicious Office file and convince them to open it.",
          "title": "According to the CVSS metric, user interaction is required (UI:R). What interaction would the user have to do?"
        },
        {
          "category": "faq",
          "text": "No, the Preview Pane is not an attack vector.",
          "title": "Is the Preview Pane an attack vector for this vulnerability?"
        },
        {
          "category": "faq",
          "text": "The security update for Microsoft Office LTSC for Mac 2021, 2024 and Microsoft 365 for Mac are not immediately available. The updates will be released as soon as possible, and when they are available, customers will be notified via a revision to this CVE information.",
          "title": "Are the updates for the Microsoft Office LTSC and Microsoft 365 for Mac currently available?"
        }
      ],
      "product_status": {
        "fixed": [
          "10739",
          "10740",
          "10836",
          "11573",
          "11574",
          "11762",
          "11763",
          "11951",
          "11952",
          "11953",
          "12420",
          "12421",
          "12440",
          "21368"
        ],
        "known_affected": [
          "1",
          "2",
          "3",
          "4",
          "5",
          "6",
          "7",
          "8",
          "9",
          "10",
          "11",
          "12",
          "13",
          "14"
        ]
      },
      "references": [
        {
          "category": "self",
          "summary": "CVE-2026-44820 Microsoft Excel Remote Code Execution Vulnerability - HTML",
          "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-44820"
        },
        {
          "category": "self",
          "summary": "CVE-2026-44820 Microsoft Excel Remote Code Execution Vulnerability - CSAF",
          "url": "https://msrc.microsoft.com/csaf/advisories/2026/msrc_cve-2026-44820.json"
        }
      ],
      "remediations": [
        {
          "category": "vendor_fix",
          "date": "2026-06-09T07:00:00.000Z",
          "details": "16.0.10417.20137:Security Update:https://support.microsoft.com/help/5002875",
          "product_ids": [
            "12"
          ],
          "url": "https://support.microsoft.com/help/5002875"
        },
        {
          "category": "vendor_fix",
          "date": "2026-06-09T07:00:00.000Z",
          "details": "https://aka.ms/OfficeSecurityReleases:Security Update:https://docs.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates",
          "product_ids": [
            "11",
            "10",
            "9",
            "8",
            "6",
            "5",
            "4",
            "3"
          ],
          "url": "https://docs.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates"
        },
        {
          "category": "vendor_fix",
          "date": "2026-06-09T07:00:00.000Z",
          "details": "16.0.5556.1001:Security Update:https://support.microsoft.com/help/5002877",
          "product_ids": [
            "14",
            "13"
          ],
          "url": "https://support.microsoft.com/help/5002877"
        }
      ],
      "scores": [
        {
          "cvss_v3": {
            "attackComplexity": "LOW",
            "attackVector": "LOCAL",
            "availabilityImpact": "HIGH",
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "HIGH",
            "environmentalsScore": 0.0,
            "exploitCodeMaturity": "UNPROVEN",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "remediationLevel": "OFFICIAL_FIX",
            "reportConfidence": "CONFIRMED",
            "scope": "UNCHANGED",
            "temporalScore": 6.8,
            "userInteraction": "REQUIRED",
            "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": [
            "1",
            "2",
            "3",
            "4",
            "5",
            "6",
            "7",
            "8",
            "9",
            "10",
            "11",
            "12",
            "13",
            "14"
          ]
        }
      ],
      "threats": [
        {
          "category": "impact",
          "details": "Remote Code Execution"
        },
        {
          "category": "exploit_status",
          "details": "Publicly Disclosed:No;Exploited:No;Latest Software Release:Exploitation Less Likely"
        }
      ],
      "title": "Microsoft Excel Remote Code Execution Vulnerability"
    }
  ]
}