Deserialization in Microsoft 365_apps
CVE-2026-21511
Deserialization of untrusted data in Microsoft Office Outlook allows an unauthorized attacker to perform spoofing over a network.
Vulnerability class: Insecure Deserialization
EPSS: 0.036 (88.1th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
Affected products
- Microsoft 365_apps
- Microsoft 365 Apps For Enterprise — versions 16.0.1
- Microsoft Office 2019 — versions 19.0.0
- Microsoft Office Ltsc 2021 — versions 16.0.1
- Microsoft Office Ltsc 2024 — versions 16.0.0
- Microsoft Office Ltsc For Mac 2021 — versions 16.0.1
- Microsoft Office Ltsc For Mac 2024 — versions 16.0.0
- Microsoft Sharepoint Enterprise Server 2016 — versions 16.0.0
- Microsoft Sharepoint Server 2019 — versions 16.0.0
- Microsoft Sharepoint Server Subscription Edition — versions 16.0.0
Weakness classification (CWE)
References
- secure@microsoft.com (vendor-advisory, patch, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-21511?
- CVE-2026-21511 is a high-severity vulnerability in Microsoft 365_apps, classified under Deserialization of Untrusted Data. CVSS score: 7.5/10. Published 2026-02-10.
- How severe is CVE-2026-21511?
- High severity. CVSS v3 base score is 7.5 out of 10.