CVE-2026-55039
HIGHCVSS 7.8/10EPSS 0.31%
Last modified
CVE-2026-55039 is a high-severity vulnerability rated 7.8/10 on the CVSS scale. Integer underflow (wrap or wraparound) 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
Integer underflow (wrap or wraparound) in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
Metrics
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-2026-55039Patch, Vendor Advisory
Timeline
- Published
- Last Modified
- Status
- Analyzed
Frequently Asked Questions
What is CVE-2026-55039?
Integer underflow (wrap or wraparound) in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
How severe is CVE-2026-55039?
CVE-2026-55039 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-2026-55039?
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-2026-55039?
Run a free Strix scan to check your systems for this vulnerability.
Scan your code nowSource: NVD / NIST