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CVE-2026-81391: Security Advisory

CVE-2026-81391 CVSS 5.5
Who it affects
See the summary below.
What to do
Apply the vendor's update in your next patch window.

CVE-2026-81391

Severity: MEDIUM (CVSS 5.5)

KEV Status: Not exploited in the wild

Affected Products:

  • Microsoft Defender Business

Description: Use of uninitialized resource in Microsoft Office Excel allows unauthorized local disclosure of information.

Remediation: Apply updates from Microsoft. See official guidance: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-81391

Impact: Local information disclosure only; no remote exploitation or authentication bypass.

Data as of September 9, 2026. Sources: nvd.nist.gov, msrc.microsoft.com. Figures are pulled from public vendor and security data and refreshed automatically.
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