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PatchSiren cyber security CVE debrief

CVE-2026-81397 Microsoft CVE debrief

Microsoft Office Excel is vulnerable to a heap-based buffer overflow, allowing an unauthorized attacker to execute code locally. This CVE was published on 2026-09-08T18:20:56.300Z and was last modified on 2026-09-17T20:18:39.400Z. The NVD entry is currently Analyzed. The vulnerability has a CVSS score of 7.8 and is classified as HIGH severity. Defenders should assess exposure and prioritize patching. The CVE record and NVD detail page provide information on the vulnerability, but do not specify affected or fixed versions.

Vendor
Microsoft
Product
Microsoft 365 Apps for Enterprise
CVSS
HIGH 7.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-09-08
Original CVE updated
2026-09-17
Advisory published
2026-09-08
Advisory updated
2026-09-17

Who should care

Defenders responsible for Microsoft Office Excel deployments should assess exposure and prioritize patching to prevent local code execution. This includes verifying exposure in Microsoft Office Excel deployments and applying patches from Microsoft. Defenders should also monitor for unauthorized access attempts and review compensating controls for exposed systems while remediation is scheduled and verified.

Why it matters

Defenders should prioritize verifying exposure in Microsoft Office Excel deployments and applying patches from Microsoft to prevent local code execution.

  • Verify exposure in Microsoft Office Excel deployments
  • Apply patches from Microsoft to prevent local code execution
  • Monitor for unauthorized access attempts

Technical summary

A heap-based buffer overflow vulnerability exists in Microsoft Office Excel, allowing an unauthorized attacker to execute code locally. The vulnerability has a CVSS score of 7.8 and is classified as HIGH severity. This vulnerability affects Microsoft Office Excel deployments, which defenders should assess for exposure and prioritize patching. The CVE record and NVD detail page provide information on the vulnerability.

Defensive priority

Defenders should prioritize verifying exposure in Microsoft Office Excel deployments and applying patches from Microsoft.

Recommended defensive actions

  • Verify exposure in Microsoft Office Excel deployments
  • Apply patches from Microsoft
  • Monitor for unauthorized access attempts

Evidence notes

The CVE record and NVD detail page provide information on the vulnerability, but do not specify affected or fixed versions. Microsoft has provided a patch and vendor advisory.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-81397 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-81397

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

  • CVE-2026-81397 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-81397

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

Supplemental references

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.