CVE-2026-69356 Microsoft Exchange Server Spoofing Vulnerability

Critical 9.3 Published 8 Sep 2026 Updated 14 Oct 2026

An attacker can perform spoofing attacks via cross-site scripting in Microsoft Exchange Server, requiring a patch to mitigate.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: A user has to click or open something
Fix: None listed

What is CVE-2026-69356?

CVE-2026-69356 is a critical cross-site scripting vulnerability in Microsoft Exchange Server, published on 8 Sep 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official description

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.

Weakness: CWE-79

Which versions are affected by CVE-2026-69356?

It affects 2 products.

Products include Microsoft Exchange Server, Microsoft Exchange Server Subscription Edition.

How do I fix CVE-2026-69356?

No fix has been published for CVE-2026-69356 yet. Limit exposure of the affected software until one is available.

Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.

Is CVE-2026-69356 being exploited?

There is no known exploitation of CVE-2026-69356 in the wild and no public exploit code.

All Microsoft Exchange Server vulnerabilities

Sources

Also known as GHSA-w4p2-9pm5-wpfw.