CVE-2026-21511
HIGHCVSS 7.5/10EPSS 3.64%
Last modified
CVE-2026-21511 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. Deserialization of untrusted data in Microsoft Office Outlook allows an unauthorized attacker to perform spoofing over a network.. EPSS estimates a 3.64% chance of exploitation in the next 30 days.
Description
Deserialization of untrusted data in Microsoft Office Outlook allows an unauthorized attacker to perform spoofing over a network.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Microsoft | 365 Apps | All versions |
| Microsoft | Office | 2019 |
| Microsoft | Office Long Term Servicing Channel | 2021 |
| Microsoft | Office Long Term Servicing Channel | 2024 |
| Microsoft | Sharepoint Server | < 16.0.19127.20518 |
| Microsoft | Sharepoint Server | 2016 |
| Microsoft | Sharepoint Server | 2019 |
| Microsoft | Word | 2016 |
References
Timeline
- Published
- Last Modified
- Status
- Analyzed
Frequently Asked Questions
What is CVE-2026-21511?
Deserialization of untrusted data in Microsoft Office Outlook allows an unauthorized attacker to perform spoofing over a network.
How severe is CVE-2026-21511?
CVE-2026-21511 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 3.64% probability of exploitation in the next 30 days.
How do I fix CVE-2026-21511?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.
How Strix Helps
- How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
- Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
- PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
- AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.
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Are you affected by CVE-2026-21511?
Run a free Strix scan to check your systems for this vulnerability.
Scan your code nowSource: NVD / NIST