CVE-2026-21511

Published: Feb 10, 2026

Modified: May 11, 2026

PUBLISHED

CVSS v3.1

7.5

HIGH

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

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

CVSS v3.1 Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

vendor-advisory

patch

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