MSRC-CVE-2026-69356 — Microsoft Exchange Server Spoofing Vulnerability

Summary

Impact: Spoofing. Microsoft rating: Important. Not known to be exploited — Exploitation Less Likely. Customer action: Required.

Details

How could an attacker exploit this vulnerability?
An unauthenticated attacker could send a specially crafted calendar invitation containing a malicious meeting link. A user would need to open the meeting and select the Join link; successful exploitation could allow script to run in the user's authenticated Outlook on the web session and access or modify mailbox data.

Security updates
15.02.1544.046 — https://support.microsoft.com/help/5121610
15.02.1748.051 — https://support.microsoft.com/help/5121609
15.02.2562.049 — https://support.microsoft.com/help/5121608
15.01.2507.073 — https://support.microsoft.com/help/5121611

Vulnerabilities 1

Critical 9.3

CVE-2026-69356

Microsoft Exchange Server Spoofing Vulnerability

Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Exchange Server allows an unauthorized attacker to perform spoofing over a network.

Microsoft Microsoft Exchange Server 2016 Cumulative Update 23 Microsoft Exchange Server Subscription Edition RTM Microsoft Exchange Server 2019 Cumulative Update 14

Sep 8, 2026

Revision history

2026-09-08 #1
Information published.

References

CVE-2026-69356 Microsoft Exchange Server Spoofing Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-69356
Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
Common Vulnerability Scoring System
https://www.first.org/cvss