CVE-2026-55009
HIGHCVSS 7.8/10EPSS 1.65%
Last modified
CVE-2026-55009 is a high-severity vulnerability rated 7.8/10 on the CVSS scale. Deserialization of untrusted data in Microsoft Exchange Server allows an authorized attacker to elevate privileges locally.. EPSS estimates a 1.65% chance of exploitation in the next 30 days.
Description
Deserialization of untrusted data in Microsoft Exchange Server allows an authorized attacker to elevate privileges locally.
Metrics
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness Enumeration
Affected Software
| Vendor | Product | Versions | Update |
|---|---|---|---|
| Microsoft | Exchange Server | 2016 | Cumulative Update 23 |
| Microsoft | Exchange Server | 2019 | Cumulative Update 14 |
| Microsoft | Exchange Server Subscription Edition | < 15.02.2562.045 | — |
References
Timeline
- Published
- Last Modified
- Status
- Analyzed
Frequently Asked Questions
What is CVE-2026-55009?
Deserialization of untrusted data in Microsoft Exchange Server allows an authorized attacker to elevate privileges locally.
How severe is CVE-2026-55009?
CVE-2026-55009 has a CVSS score of 7.8/10 (HIGH severity). The EPSS model estimates a 1.65% probability of exploitation in the next 30 days.
How do I fix CVE-2026-55009?
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-2026-55009?
Run a free Strix scan to check your systems for this vulnerability.
Scan your code nowSource: NVD / NIST