CVE-2026-81399 Microsoft CVE debrief

Who should care

Defenders responsible for Microsoft Office Excel installations should assess exposure and prioritize verification of vulnerable versions. They should also apply patches if available to prevent potential local information disclosure. This includes reviewing the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance, and planning vendor-supported updates or mitigations.

Why it matters

CVE-2026-81399 is a buffer over-read vulnerability in Microsoft Office Excel that could allow local information disclosure. Defenders should assess exposure, prioritize verification of vulnerable versions, and apply patches if available to prevent potential local information disclosure.

• Assess exposure of Microsoft Office Excel installations
• Prioritize verification of vulnerable versions
• Apply patches if available to prevent local information disclosure

Technical summary

A buffer over-read vulnerability in Microsoft Office Excel could allow an unauthorized attacker to disclose information locally. The vulnerability has a CVSS score of 5.5 and a severity of MEDIUM. This vulnerability affects Microsoft Office Excel installations, and defenders should assess exposure and prioritize verification of vulnerable versions to prevent potential local information disclosure.

Defensive priority

Assess exposure of Microsoft Office Excel installations, prioritize verification of vulnerable versions, and apply patches if available.

Recommended defensive actions

• Assess exposure of Microsoft Office Excel installations
• Prioritize verification of vulnerable versions
• Apply patches if available
• Monitor for potential local information disclosure

Evidence notes

The CVE record and NVD detail page provide information on the vulnerability, but do not specify versions or provide additional details on exploitation.

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.