CVE-2026-21511

HighCVSS 7.5/10Last modified Jun 17, 2026

Description

Deserialization of untrusted data in Microsoft Office Outlook allows an unauthorized attacker to perform spoofing over a network.

Metrics

CVSS 3.1 7.5/10CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Weakness enumeration

CWE-502

Affected software

Vendor	Product	Versions
Microsoft	Microsoft 365 Apps for Enterprise	>= 16.0.1, < https://aka.ms/OfficeSecurityReleases
Microsoft	Microsoft Office 2019	>= 19.0.0, < https://aka.ms/OfficeSecurityReleases
Microsoft	Microsoft Office LTSC 2021	>= 16.0.1, < https://aka.ms/OfficeSecurityReleases
Microsoft	Microsoft Office LTSC 2024	>= 16.0.0, < https://aka.ms/OfficeSecurityReleases
Microsoft	Microsoft Office LTSC for Mac 2021	>= 16.0.1, < 16.106.26020821
Microsoft	Microsoft Office LTSC for Mac 2024	>= 16.0.0, < 16.106.26020821
Microsoft	Microsoft SharePoint Enterprise Server 2016	>= 16.0.0, < 16.0.5539.1002
Microsoft	Microsoft SharePoint Server 2019	>= 16.0.0, < 16.0.10417.20097
Microsoft	Microsoft SharePoint Server Subscription Edition	>= 16.0.0, < 16.0.19127.20518
Microsoft	Microsoft Word 2016	>= 16.0.1, < 16.0.5539.1002

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21511Vendor Advisory

Timeline

Published: Feb 10, 2026
Last modified: Jun 17, 2026
NVD status: Analyzed

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