CVE-2026-81400 Microsoft CVE debrief

Who should care

Defenders and administrators responsible for Microsoft Office Excel installations should assess exposure and apply patches to prevent local information disclosure. They should also verify and apply patches from Microsoft and monitor for local unauthorized access attempts. Inventory checks are necessary to identify potentially affected Microsoft Office Excel installations. This vulnerability affects Microsoft Office,

Why it matters

CVE-2026-81400 is a MEDIUM-severity vulnerability in Microsoft Office Excel that allows local information disclosure. Defenders and administrators should assess exposure, verify and apply patches, and monitor for local unauthorized access attempts.

• Local information disclosure is possible due to the out-of-bounds read vulnerability
• Defenders should verify and apply patches from Microsoft to prevent exposure
• Inventory checks are necessary to identify potentially affected Microsoft Office Excel installations

Technical summary

CVE-2026-81400 is an out-of-bounds read vulnerability in Microsoft Office Excel, allowing local information disclosure. The vulnerability has a CVSS score of 5.5 and is classified as MEDIUM severity. It is essential for defenders and administrators to assess exposure, verify and apply patches from Microsoft, and monitor for local unauthorized access attempts to prevent information disclosure.

Defensive priority

Assess exposure and apply patches for Microsoft Office Excel

Recommended defensive actions

• Inventory Microsoft Office Excel installations for potential exposure
• Verify and apply patches from Microsoft
• Monitor for local unauthorized access attempts

Evidence notes

The CVE record and NVD entry provide details on the vulnerability. However, specific version information and remediation steps require verification from official sources.

Sources and 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.