CVE-2026-55039

Integer underflow (wrap or wraparound) in Microsoft Office Excel allows an unauthorized attacker to execute code locally.

CVSS v3 7.8 HIGH

7.8^/10

CVSS v3 : HIGH

Vector :

Exploitability : 1.8 / Impact : 5.9

Attack Vector LOCAL

Attack Complexity LOW

Privileges Required NONE

User Interaction REQUIRED

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55039	Patch Vendor Advisory

Configurations

Configuration 1 (hide)

OR	cpe:2.3:a:microsoft:365_apps:-::::enterprise::x64:*
	cpe:2.3:a:microsoft:365_apps:-::::enterprise::x86:*
	cpe:2.3:a:microsoft:excel:2016::::::x64:
	cpe:2.3:a:microsoft:excel:2016::::::x86:
	cpe:2.3:a:microsoft:microsoft_365:-:::::macos::
	cpe:2.3:a:microsoft:office_2019:-::::::x64:
	cpe:2.3:a:microsoft:office_2019:-::::::x86:
	cpe:2.3:a:microsoft:office_2021:-::::ltsc:-:x64:
	cpe:2.3:a:microsoft:office_2021:-::::ltsc:-:x86:
	cpe:2.3:a:microsoft:office_2021:-::::ltsc:macos:-:
	cpe:2.3:a:microsoft:office_2024:-::::ltsc:-:x64:
	cpe:2.3:a:microsoft:office_2024:-::::ltsc:-:x86:
	cpe:2.3:a:microsoft:office_2024:-::::ltsc:macos:-:
	cpe:2.3:a:microsoft:office_online_server::::::::

History

No history.

Information

Published : 2026-07-14 18:18

Updated : 2026-07-16 14:18

NVD link : CVE-2026-55039

Mitre link : CVE-2026-55039

CVE.ORG link : CVE-2026-55039

JSON object : View

Products Affected

microsoft

office_2024
office_2019
microsoft_365
excel
365_apps
office_2021
office_online_server

CWE

CWE-122

Heap-based Buffer Overflow

CWE-191

Integer Underflow (Wrap or Wraparound)

{"id": "CVE-2026-55039", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-55039", "role": "CISA Coordinator", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "total"}], "version": "2.0.3", "timestamp": "2026-07-10T00:00:00+00:00"}}], "cvssMetricV31": [{"type": "Secondary", "source": "secure@microsoft.com", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 7.8, "attackVector": "LOCAL", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H", "integrityImpact": "HIGH", "userInteraction": "REQUIRED", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "HIGH"}, "impactScore": 5.9, "exploitabilityScore": 1.8}]}, "affected": [{"source": "secure@microsoft.com", "affectedData": [{"vendor": "Microsoft", "product": "Microsoft 365 Apps for Enterprise", "versions": [{"status": "affected", "version": "16.0.1", "lessThan": "https://aka.ms/OfficeSecurityReleases", "versionType": "custom"}], "platforms": ["32-bit Systems", "x64-based Systems"]}, {"vendor": "Microsoft", "product": "Microsoft Excel 2016", "versions": [{"status": "affected", "version": "16.0.0.0", "lessThan": "16.0.5561.1001", "versionType": "custom"}], "platforms": ["32-bit Systems", "x64-based Systems"]}, {"vendor": "Microsoft", "product": "Microsoft Office 2019", "versions": [{"status": "affected", "version": "19.0.0", "lessThan": "https://aka.ms/OfficeSecurityReleases", "versionType": "custom"}], "platforms": ["32-bit Systems", "x64-based Systems"]}, {"vendor": "Microsoft", "product": "Microsoft Office 365 for Mac", "versions": [{"status": "affected", "version": "1.0.0", "lessThan": "16.111.26071215", "versionType": "custom"}]}, {"vendor": "Microsoft", "product": "Microsoft Office LTSC 2021", "versions": [{"status": "affected", "version": "16.0.1", "lessThan": "https://aka.ms/OfficeSecurityReleases", "versionType": "custom"}], "platforms": ["32-bit Systems", "x64-based Systems"]}, {"vendor": "Microsoft", "product": "Microsoft Office LTSC 2024", "versions": [{"status": "affected", "version": "16.0.0", "lessThan": "https://aka.ms/OfficeSecurityReleases", "versionType": "custom"}], "platforms": ["32-bit Systems", "x64-based Systems"]}, {"vendor": "Microsoft", "product": "Microsoft Office LTSC for Mac 2021", "versions": [{"status": "affected", "version": "16.0.1", "lessThan": "16.111.26071215", "versionType": "custom"}]}, {"vendor": "Microsoft", "product": "Microsoft Office LTSC for Mac 2024", "versions": [{"status": "affected", "version": "16.0.0", "lessThan": "16.111.26071215", "versionType": "custom"}]}, {"vendor": "Microsoft", "product": "Office Online Server", "versions": [{"status": "affected", "version": "16.0.0.0", "lessThan": "16.0.10417.20175", "versionType": "custom"}]}]}], "published": "2026-07-14T18:18:15.257", "references": [{"url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55039", "tags": ["Patch", "Vendor Advisory"], "source": "secure@microsoft.com"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Secondary", "source": "secure@microsoft.com", "description": [{"lang": "en", "value": "CWE-122"}, {"lang": "en", "value": "CWE-191"}]}], "descriptions": [{"lang": "en", "value": "Integer underflow (wrap or wraparound) in Microsoft Office Excel allows an unauthorized attacker to execute code locally."}], "lastModified": "2026-07-16T14:18:09.780", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:microsoft:365_apps:-:*:*:*:enterprise:*:x64:*", "vulnerable": true, "matchCriteriaId": "3259EBFE-AE2D-48B8-BE9A-E22BBDB31378"}, {"criteria": "cpe:2.3:a:microsoft:365_apps:-:*:*:*:enterprise:*:x86:*", "vulnerable": true, "matchCriteriaId": "CD25F492-9272-4836-832C-8439EBE64CCF"}, {"criteria": "cpe:2.3:a:microsoft:excel:2016:*:*:*:*:*:x64:*", "vulnerable": true, "matchCriteriaId": "CD88F667-6773-4DB7-B6C3-9C7B769C0808"}, {"criteria": "cpe:2.3:a:microsoft:excel:2016:*:*:*:*:*:x86:*", "vulnerable": true, "matchCriteriaId": "B342EF98-B414-44D0-BAFB-FCA24294EECE"}, {"criteria": "cpe:2.3:a:microsoft:microsoft_365:-:*:*:*:*:macos:*:*", "vulnerable": true, "matchCriteriaId": "12418BDE-FA2E-4BBF-8E47-45C505399898"}, {"criteria": "cpe:2.3:a:microsoft:office_2019:-:*:*:*:*:*:x64:*", "vulnerable": true, "matchCriteriaId": "241CDE2B-ABD0-4EFF-8D73-1766E32FA20F"}, {"criteria": "cpe:2.3:a:microsoft:office_2019:-:*:*:*:*:*:x86:*", "vulnerable": true, "matchCriteriaId": "14D63E3F-A431-4DD8-979F-811E8DAC423D"}, {"criteria": "cpe:2.3:a:microsoft:office_2021:-:*:*:*:ltsc:-:x64:*", "vulnerable": true, "matchCriteriaId": "1D518075-3362-4D15-93B1-0E6C61518D16"}, {"criteria": "cpe:2.3:a:microsoft:office_2021:-:*:*:*:ltsc:-:x86:*", "vulnerable": true, "matchCriteriaId": "1059BEC6-C30B-4F0F-A878-5267A21CBD85"}, {"criteria": "cpe:2.3:a:microsoft:office_2021:-:*:*:*:ltsc:macos:-:*", "vulnerable": true, "matchCriteriaId": "0DB3EBBF-E0C4-4D5A-8D22-107463AD1DE4"}, {"criteria": "cpe:2.3:a:microsoft:office_2024:-:*:*:*:ltsc:-:x64:*", "vulnerable": true, "matchCriteriaId": "55A9AFDA-D77B-4CC7-ACE5-3A2ABDA257D8"}, {"criteria": "cpe:2.3:a:microsoft:office_2024:-:*:*:*:ltsc:-:x86:*", "vulnerable": true, "matchCriteriaId": "8887D177-26A3-4008-89B6-50A9E9830F13"}, {"criteria": "cpe:2.3:a:microsoft:office_2024:-:*:*:*:ltsc:macos:-:*", "vulnerable": true, "matchCriteriaId": "589B470B-9C2E-41E2-A44D-D8CCB4D2F933"}, {"criteria": "cpe:2.3:a:microsoft:office_online_server:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "746CEA14-C3AC-4256-A71D-BCA3A43459F8", "versionEndExcluding": "16.0.10417.20175"}], "operator": "OR"}]}], "sourceIdentifier": "secure@microsoft.com"}