Microsoft Security Response CenterCVE-2026-56191

Microsoft Exchange Online Tampering Vulnerability

CriticalVendor CVSS 10.0 / 10 1 CVE Published Jul 23, 2026 at 7:00 AM UTC

Summary

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

Separate remediation guidance was not included in the collected bulletin.

Jul 23, 2026 at 7:00 AM UTC
Published by Microsoft Security Response Center
The publication date reported by the vendor.
Sep 28, 2026 at 11:20 AM UTC
Added to SecurityAlert
We collected the advisory from the official source.
Nov 11, 2026 at 2:20 AM UTC
Confirmed at the source
Our collector saw this advisory during a later source check.

Details collected from Microsoft Security Response Center.

Official bulletin How SecurityAlert builds this record

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