CVE-2026-21511

Published: Feb 10, 2026Modified: Feb 11, 2026

7.5

Vector

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

Exploitability: 3.9 / Impact: 3.6

Source: secure@microsoft.com

Description

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

Affected (15)

Products: Microsoft: 365 Apps, Office, Office Long Term Servicing Channel, Sharepoint Server, Word

5 products

Office Long Term Servicing Channel

Sharepoint Server

Configuration A

15 vulnerable

Vulnerable Software	Affected Versions
Microsoft 365 Apps	All versions
Microsoft 365 Apps	All versions
Microsoft Office	Version 2019
Microsoft Office	Version 2019
Microsoft Office Long Term Servicing Channel	Version 2021
Microsoft Office Long Term Servicing Channel	Version 2021
Microsoft Office Long Term Servicing Channel	Version 2021
Microsoft Office Long Term Servicing Channel	Version 2024
Microsoft Office Long Term Servicing Channel	Version 2024
Microsoft Office Long Term Servicing Channel	Version 2024
Microsoft Sharepoint Server	Before 16.0.19127.20518
Microsoft Sharepoint Server	Version 2016
Microsoft Sharepoint Server	Version 2019
Microsoft Word	Version 2016
Microsoft Word	Version 2016

Related CWEs

Deserialization of Untrusted Data

The product deserializes untrusted data without sufficiently verifying that the resulting data will be valid.

References (1)

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

Source: secure@microsoft.com

Vendor Advisory

Timeline

No history available yet.