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CVE-2026-64903 Microsoft CVE debrief

Microsoft Office Remote Code Execution Vulnerability allows an unauthorized attacker to execute code locally due to an integer overflow or wraparound in Microsoft Office. This vulnerability affects Microsoft Office deployments, and defenders should assess exposure and prioritize patching. The CVE record and NVD entry provide details on the vulnerability, but do not specify versions or exploitation details. Defenders should verify exposure across their inventory and monitor for suspicious activity.

Vendor
Microsoft
Product
Microsoft 365 Apps for Enterprise
CVSS
HIGH 7.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-08-11
Original CVE updated
2026-10-08
Advisory published
2026-08-11
Advisory updated
2026-10-08

Who should care

Defenders responsible for Microsoft Office deployments should assess exposure and prioritize patching. They should verify exposure across their inventory and monitor for suspicious activity. Defenders should also review compensating controls for exposed systems while remediation is scheduled and verified.

Why it matters

CVE-2026-64903 allows local code execution; defenders should prioritize patching and verify exposure across their inventory.

  • Verify patching priority for vulnerable Microsoft Office versions
  • Assess exposure across inventory
  • Monitor for suspicious activity

Technical summary

Integer overflow or wraparound in Microsoft Office allows an unauthorized attacker to execute code locally. The vulnerability affects Microsoft Office deployments, and defenders should assess exposure and prioritize patching. The CVE record and NVD entry provide details on the vulnerability, but do not specify versions or exploitation details. Defenders should verify exposure across their inventory and monitor for suspicious activity.

Defensive priority

Defenders should prioritize patching vulnerable Microsoft Office versions and verify exposure across their inventory.

Recommended defensive actions

  • Patch vulnerable Microsoft Office versions
  • Verify exposure across inventory
  • Monitor for suspicious activity

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, but do not specify versions or exploitation details. The vulnerability affects Microsoft Office, and defenders should verify exposure across their inventory. The source item providing details on the vulnerability also does not specify versions or exploitation details. Defenders should prioritize patching vulnerable Microsoft Office versions and verify exposure across their inventory.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-64903 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-64903

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-64903 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-64903

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Microsoft Office Remote Code Execution Vulnerability

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/64xxx/CVE-2026-64903.json

    cve_program_cvelist_v5

  • Source reference

    Unverified legacy reference

    URL: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-64903

    Supplemental source - vendor-advisory, patch

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.