CVE-2026-42897 Microsoft Exchange Server Cross-Site Scripting

Exploited in the wild High 8.1 Published 14 May 2026 Updated 10 Aug 2026

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

Exploited in the wild: Since 15 May 2026
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-2026-42897?

CVE-2026-42897 is a high-severity cross-site scripting vulnerability in Microsoft Exchange Server, published on 14 May 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-2026-42897?

It affects 2 products.

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

How do I fix CVE-2026-42897?

No fix has been published for CVE-2026-42897 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 29 May 2026.

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-2026-42897 being exploited?

Yes. Attackers have exploited CVE-2026-42897 in the wild since at least 15 May 2026.

Public exploit code: 1 proofs of concept on GitHub.

All Microsoft Exchange Server vulnerabilities

Sources

Also known as GHSA-3c39-338m-m4vp.