CVE-2026-62911: Microsoft Exchange Server Elevation of Privilege Vulnerability

Overview

Severity

High (CVSS 8)

CVSS Vector

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

Category

Elevation of Privilege

Exploit Status

Not Exploited

Exploitation Likelihood

Less Likely

Patch Tuesday

2026-Aug

Released

2026-08-11

Description

Authentication bypass by capture-replay in Microsoft Exchange Server allows an authorized attacker to elevate privileges over a network.

FAQ

What privileges could be gained by an attacker who successfully exploited the vulnerability? The attacker would be able to take over the mailboxes of all Exchange users, attackers can send emails, read emails, download attachments.

Affected Products (4)

ESU

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

Server Software

• Microsoft Exchange Server Subscription Edition RTM

Security Updates (1)

• 5121573

Acknowledgments

<a href="https://linkedin.com/in/dr-sr">Dan Reynolds</a> with MSRC Vulnerabilities &amp; Mitigations, Orange Tsai (@orange_8361) of DEVCORE Research Team working with TrendAI Zero Day Initiative

Revision History

• 2026-08-11: Information published.