What is CVE-2026-56191?

CVE-2026-56191 is a security advisory published by Microsoft Security Response Center (MSRC) with Critical severity. Microsoft Exchange Online Tampering Vulnerability

Which CVE IDs does CVE-2026-56191 cover?

CVE-2026-56191 covers the following CVE IDs: CVE-2026-56191. Each CVE has its own detail page on EchelonGraph Pulse with the synthesized EG score.

What is the CVSS v3 score of CVE-2026-56191?

CVE-2026-56191 has a CVSS v3 base score of 10.0, published by Microsoft Security Response Center (MSRC).

Which products are affected by CVE-2026-56191?

CVE-2026-56191 affects 1 product, including: Microsoft Exchange Online.

CVE-2026-56191CriticalCVSS 10.0

Microsoft Exchange Online Tampering Vulnerability

Vendor

Microsoft Security Response Center (MSRC)

Published

July 23, 2026

Last Modified

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🔗 CVE IDs covered (1)

CVE-2026-56191 →

📋 Description

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

🎯 Affected products1

Microsoft Exchange Online

🔗 References (1)

advisoryhttps://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56191