CVE-2026-56191
CRITICALCVSS 10/10EPSS 0.68%
Last modified
CVE-2026-56191 is a critical-severity vulnerability rated 10/10 on the CVSS scale. Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform tampering over a network.. EPSS estimates a 0.68% chance of exploitation in the next 30 days.
Description
Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform tampering over a network.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Microsoft | Exchange Online | All versions |
References
Timeline
- Published
- Last Modified
- Status
- Analyzed
Frequently Asked Questions
What is CVE-2026-56191?
Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform tampering over a network.
How severe is CVE-2026-56191?
CVE-2026-56191 has a CVSS score of 10/10 (CRITICAL severity). The EPSS model estimates a 0.68% probability of exploitation in the next 30 days.
How do I fix CVE-2026-56191?
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-2026-56191?
Run a free Strix scan to check your systems for this vulnerability.
Scan your code nowSource: NVD / NIST