ZDI-26-534: (Pwn2Own) Microsoft Exchange Capture-Replay Authentication Bypass Vulnerability

Published Aug 11, 2026
·
Updated

This vulnerability allows remote attackers to bypass authentication on affected installations of Microsoft Exchange. Authentication is not required to exploit this vulnerability. The ZDI has assigned a CVSS rating of 8.1. The following CVEs are assigned: CVE-2026-62911.

Affected Software

1 affected component
Microsoft Microsoft Exchange

Event History

Aug 11, 2026
Advisory Published
via ZDI·05:00 AM
Data Sourced
via ZDI·05:00 AM
Description
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Frequently Asked Questions

1

What is the severity of ZDI-26-534?

ZDI-26-534 has a CVSS rating of 8.1, indicating a high severity vulnerability.

2

How do I fix ZDI-26-534?

To fix ZDI-26-534, ensure that you apply the latest security patches provided by Microsoft for affected versions of Exchange.

3

What systems are affected by ZDI-26-534?

ZDI-26-534 affects installations of Microsoft Exchange that are not updated with the latest security patches.

4

Can ZDI-26-534 be exploited remotely?

Yes, ZDI-26-534 can be exploited remotely without authentication.

5

What is the consequence of ZDI-26-534 being exploited?

If exploited, ZDI-26-534 allows attackers to bypass authentication, potentially leading to unauthorized access to sensitive information.

Contact

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