Review reviewHigh

CVE-2026-55949

Microsoft Microsoft 365 Apps for Enterprise, Microsoft Excel 2016, Microsoft Office 2019

Use of uninitialized resource in Microsoft Office Excel allows an unauthorized attacker to execute code locally.

PRIORITY ASSESSMENT

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV

Exploit probability0.30%

Technical severityCVSS 7.8

Use of uninitialized resource in Microsoft Office Excel allows an unauthorized attacker to execute code locally.

Product: Microsoft Microsoft 365 Apps for Enterprise, Microsoft Excel 2016, Microsoft Office 2019
Affected versions: >= 16.0.1 < https://aka.ms/OfficeSecurityReleases, >= 16.0.0.0 < 16.0.5561.1001, >= 19.0.0 < https://aka.ms/OfficeSecurityReleases, >= 1.0.0 < 16.111.26071215, >= 16.0.0 < https://aka.ms/OfficeSecurityReleases, >= 16.0.1 < 16.111.26071215, >= 16.0.0 < 16.111.26071215, >= 16.0.0.0 < 16.0.10417.20175, 2016, < 16.0.10417.20175
Fixed versions: 16.0.10417.20175

Confirm exposure before applying a vendor-supported change.

1
Identify
Confirm that Microsoft Microsoft 365 Apps for Enterprise, Microsoft Excel 2016, Microsoft Office 2019 and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.