Vulnerability · Published Feb 10, 2026 · Assigned by microsoft
CVE-2026-21511Microsoft Outlook Spoofing Vulnerability
High 7.5
In plain English
A high-severity unsafe deserialization in Microsoft 365 Apps for Enterprise from Microsoft. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 4.0% (higher than 91% of all known vulnerabilities).
Severity (CVSS 3.1)7.5High
Exploit odds (30 days)4.0%top 9.5% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
Deserialization of untrusted data in Microsoft Office Outlook allows an unauthorized attacker to perform spoofing over a network.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Microsoft | Microsoft 365 Apps for Enterprise | 16.0.1 – before https://aka.ms/OfficeSecurityReleases |
| Microsoft | Microsoft Office 2019 | 19.0.0 – before https://aka.ms/OfficeSecurityReleases |
| Microsoft | Microsoft Office LTSC 2021 | 16.0.1 – before https://aka.ms/OfficeSecurityReleases |
| Microsoft | Microsoft Office LTSC 2024 | 16.0.0 – before https://aka.ms/OfficeSecurityReleases |
| Microsoft | Microsoft Office LTSC for Mac 2021 | 16.0.1 – before 16.106.26020821 |
| Microsoft | Microsoft Office LTSC for Mac 2024 | 16.0.0 – before 16.106.26020821 |
| Microsoft | Microsoft SharePoint Enterprise Server 2016 | 16.0.0 – before 16.0.5539.1002 |
| Microsoft | Microsoft SharePoint Server 2019 | 16.0.0 – before 16.0.10417.20097 |
| Microsoft | Microsoft SharePoint Server Subscription Edition | 16.0.0 – before 16.0.19127.20518 |
| Microsoft | Microsoft Word 2016 | 16.0.1 – before 16.0.5539.1002 |
Weakness: CWE-502 · 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
References
- Microsoft Outlook Spoofing Vulnerability vendor-advisory, patch