Weak Authentication in Microsoft Exchange Server - CVE-2026-96940
Published: October 13, 2026
Vulnerability identifier: #VU154225
CSH Severity: Low
CVSS v4: 7.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-96940
CWE-ID: CWE-1390
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to disclose sensitive information.
The vulnerability exists due to weak authentication in Microsoft Exchange Outlook Web Access (OWA) when handling web requests. A remote user can gain unauthorized access to other users' mailboxes and read email messages and attachments to disclose sensitive information.
Mailbox access is limited to users within the same organization; the vulnerability does not allow access across tenant boundaries.
Affected software
Microsoft Exchange Server
How to mitigate CVE-2026-96940
Install security update from vendor's website.
Microsoft Exchange Server - addressed in versions SE RTM Sep26SUv2 15.02.2562.053, 2016 CU23 Sep26SUv2 15.01.2507.075, 2019 CU14 Sep26SUv2 15.02.1544.048, 2019 CU15 Sep26SUv2 15.02.1748.053