CVE-2026-78509
CRITICALCVSS 9.8/10EPSS 0.95%
Last modified
CVE-2026-78509 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.. EPSS estimates a 0.95% chance of exploitation in the next 30 days.
Description
Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.
Metrics
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Microsoft | 365 Apps | All versions |
| Microsoft | Microsoft 365 | All versions |
| Microsoft | Office 2019 | All versions |
| Microsoft | Office 2021 | All versions |
| Microsoft | Office 2024 | All versions |
| Microsoft | Word | 2016 |
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78509Patch, Vendor Advisory
Timeline
- Published
- Last Modified
- Status
- Analyzed
Frequently Asked Questions
What is CVE-2026-78509?
Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.
How severe is CVE-2026-78509?
CVE-2026-78509 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 0.95% probability of exploitation in the next 30 days.
How do I fix CVE-2026-78509?
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-2026-78509?
Run a free Strix scan to check your systems for this vulnerability.
Scan your code nowSource: NVD / NIST