CVE-2026-56191

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

Score

CVSS 3.1 10.0 Critical

Status

Analyzed - secure@microsoft.com

Published

2026-07-24

Last modified

2026-10-28

Weaknesses

CWE-287

Affected products

• Exchange Online (Microsoft)

References

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