CVE intelligence

CVE-2026-56191

Vulnerability intelligence

Published Jul 24, 2026Sources checked Sep 28, 2026

10.0CRITICALCVSS out of 10

What this means

Review the available evidence

CVE-2026-56191 and is rated Critical severity with a CVSS score of 10.0. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

CISA KEVNot listedBased on the latest collected catalog

EPSS0.9%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is CVE-2026-56191?

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