CVE-2026-56191

CRITICAL CVSS 3.1: 10.0 EPSS 0.68%
Updated Jul 25, 2026
Microsoft
Parameter Value
CVSS 10.0 (CRITICAL)
Type CWE-287 (Improper Authentication)
Vendor Microsoft
Public PoC No

Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform tampering over a network.

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed

Impact Assessment

Confidentiality
High
Complete data leak
Integrity
High
Complete data modification
Availability
High
Complete denial of service

CVSS Vector v3.1