Improper Authentication Vulnerability in Microsoft Exchange Online
CVE-2026-56191

10CRITICAL

Key Information:

Vendor

Microsoft
Status
Microsoft Exchange Online
Vendor
CVE Published:
24 July 2026

What is CVE-2026-56191?

An improper authentication vulnerability exists in Microsoft Exchange Online that could allow an unauthorized attacker to manipulate data over a network, potentially impacting data integrity and confidentiality. This flaw requires immediate attention and remediation to secure communications and maintain user trust.

Affected Version(s)

Microsoft Exchange Online -

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE...
vendor-advisorypatch

CVSS V3.1

Score:
10
Severity:
CRITICAL
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Changed

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.