CVE-2026-69378: Microsoft Exchange Server Denial of Service Vulnerability

Overview

Severity

High (CVSS 7.5)

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C

Category

Denial of Service

Exploit Status

Not Exploited

Exploitation Likelihood

Less Likely

Patch Tuesday

2026-Sep

Released

2026-09-08

Description

Uncontrolled recursion in Microsoft Exchange Server allows an unauthorized attacker to deny service over a network.

Affected Products (4)

ESU

• Microsoft Exchange Server 2016 Cumulative Update 23
• Microsoft Exchange Server 2019 Cumulative Update 14
• Microsoft Exchange Server 2019 Cumulative Update 15

Server Software

• Microsoft Exchange Server Subscription Edition RTM

Security Updates (1)

• 5121608

Acknowledgments

<a href="https://www.linkedin.com/in/yannic-r-28b446158/">Yannic R&#246;cken</a> with <a href="https://indeno.at/">Indeno GmbH</a>

Revision History

• 2026-09-08: Information published.