Deserialization Vulnerability in Microsoft Office Outlook
CVE-2026-21511

7.5HIGH

Key Information:

Vendor

Microsoft
Status
Microsoft 365 Apps For Enterprise
Microsoft Office 2019
Microsoft Office Ltsc 2021
Microsoft Office Ltsc 2024
Vendor
CVE Published:
10 February 2026

What is CVE-2026-21511?

A deserialization vulnerability in Microsoft Office Outlook enables an attacker to exploit untrusted data, leading to potential network spoofing attacks. This security flaw could allow unauthorized individuals to impersonate legitimate users and intercept communication, posing a significant threat to data integrity and confidentiality.

Affected Version(s)

Microsoft 365 Apps for Enterprise 32-bit Systems 16.0.1

Microsoft Office 2019 32-bit Systems 19.0.0

Microsoft Office LTSC 2021 32-bit Systems 16.0.1

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE...
vendor-advisorypatch

CVSS V3.1

Score:
7.5
Severity:
HIGH
Confidentiality:
High
Integrity:
None
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.