CVE-2026-21511 json
Microsoft Outlook Spoofing Vulnerability
published 8mo ago modified 2mo ago also EUVD-2026-7331
- cvss
- 7.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 4.0%
- EPSS 4.0% chance of exploitation in 30 days, percentile 90%
- public exploits
- 0
- none known
Summary
Deserialization of untrusted data in Microsoft Office Outlook allows an unauthorized attacker to perform spoofing over a network.
Patch / fix
- Microsoft Microsoft Office LTSC for Mac 2021 16.106.26020821
- Microsoft Microsoft Office LTSC for Mac 2024 16.106.26020821
- Microsoft Microsoft SharePoint Enterprise Server 2016 16.0.5539.1002
- Microsoft Microsoft SharePoint Server 2019 16.0.10417.20097
- Microsoft Microsoft SharePoint Server Subscription Edition 16.0.19127.20518
- Microsoft Microsoft Word 2016 16.0.5539.1002
Is CVE-2026-21511 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 8mo ago
Exploit prediction
3.97% chance of exploitation in the next 30 days, higher than 90% of all scored CVEs (FIRST EPSS, 2026-11-09).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 7.5 | 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 |
| CNA | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N |
Affected products
- Microsoft Microsoft 365 Apps for Enterprise
- Microsoft Microsoft Office 2019
- Microsoft Microsoft Office LTSC 2021
- Microsoft Microsoft Office LTSC 2024
- Microsoft Microsoft Office LTSC for Mac 2021
- Microsoft Microsoft Office LTSC for Mac 2024
- Microsoft Microsoft SharePoint Enterprise Server 2016
- Microsoft Microsoft SharePoint Server 2019
- Microsoft Microsoft SharePoint Server Subscription Edition
- Microsoft Microsoft Word 2016
Classification
- Weakness
-
- CWE-502 Deserialization of Untrusted Data
References
-
msrc.microsoft.com
/update-guide/vulnerability/CVE-2026-21511
vendor-advisory, patch
Sources
- CVE List CVE-2026-21511
- NVD CVE-2026-21511
Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.