CVE-2026-56191 Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform tampering over a network

Description

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

Affected products and versions

Product	Affected versions	Fixed in
Microsoft Exchange Online	Versions not published

Other CVEs of Microsoft Exchange Online

The 7 CVEs of Microsoft Exchange Online →

CVE-2026-96185 Stack-based buffer overflow in Microsoft Exchange Online allows an authorized attacker to execute code over a network 7.5 High CVE-2026-65801 Server-side request forgery (ssrf) in Microsoft Exchange Online allows an unauthorized attacker to elevate privileges… 10.0 Critical CVE-2026-54998 Incorrect authorization in Microsoft Exchange Online allows an authorized attacker to elevate privileges over a network 8.8 High CVE-2026-48582 Missing authorization in Microsoft Exchange Online allows an authorized attacker to elevate privileges over a network 9.6 Critical