CVE-2026-55899
HIGHCVSS 7.8/10EPSS 0.31%
Last modified
CVE-2026-55899 is a high-severity vulnerability rated 7.8/10 on the CVSS scale. Stack-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code locally.. EPSS estimates a 0.31% chance of exploitation in the next 30 days.
Description
Stack-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
Metrics
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Microsoft | 365 Apps | All versions |
| Microsoft | Excel | 2016 |
| Microsoft | Microsoft 365 | All versions |
| Microsoft | Office 2019 | All versions |
| Microsoft | Office 2021 | All versions |
| Microsoft | Office 2024 | All versions |
| Microsoft | Office Online Server | < 16.0.10417.20175 |
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55899Patch, Vendor Advisory
Timeline
- Published
- Last Modified
- Status
- Analyzed
Frequently Asked Questions
What is CVE-2026-55899?
Stack-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
How severe is CVE-2026-55899?
CVE-2026-55899 has a CVSS score of 7.8/10 (HIGH severity). The EPSS model estimates a 0.31% probability of exploitation in the next 30 days.
How do I fix CVE-2026-55899?
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-2026-55899?
Run a free Strix scan to check your systems for this vulnerability.
Scan your code nowSource: NVD / NIST