CVE-2026-42897 Microsoft Microsoft: web page flaw
In plain words: A web app can be made to act on someone's behalf or reach places it should not. Stolen sessions, actions taken as the victim, or access to internal systems.
Confirmed exploited by CISA on · US federal patch deadline May 29, 2026
What to do
- Install Microsoft's security update for Microsoft. If no update exists, follow the vendor's workaround or stop using the product until one ships.
- Keep a list of every internet-facing server you run so nothing is forgotten.
- Patch anything in this catalog first, ahead of normal patch cycles.
- Put admin and file-transfer apps behind a VPN or single sign-on instead of the open internet.
Who is affected
Work IT. Aimed mostly at company systems — you are affected through the companies you use, not your own phone.
What's at risk: Mass data theft and ransomware: a single flaw in a file-transfer or email server has exposed thousands of organisations at once.
The details
- Official name
- Microsoft Exchange Server Cross-Site Scripting Vulnerability
- Product
- Microsoft Microsoft
- CISA description
- Microsoft Exchange Server contains a cross-site scripting vulnerability during web page generation in Outlook Web Access and when certain interaction conditions are met, arbitrary JavaScript can be executed in the browser context.
- Type of flaw
- Web page flaw (CWE-79)
- Confirmed exploited
- May 15, 2026
- US federal patch deadline
- May 29, 2026
Ask Cleus about it
Ask about a vulnerability, an update, a weird message, or the news. Plain-word answers, free, no account.
Answering about CVE-2026-42897 ·
Questions about CVE-2026-42897
Is CVE-2026-42897 being exploited?
Yes. CISA added CVE-2026-42897 to its Known Exploited Vulnerabilities catalog on May 15, 2026, which means there is reliable evidence of real-world attacks.
How do I fix CVE-2026-42897?
Install Microsoft's security update for Microsoft. If no update exists, follow the vendor's workaround or stop using the product until one ships. Keep a list of every internet-facing server you run so nothing is forgotten.
Am I affected by CVE-2026-42897?
Only if you use Microsoft Microsoft. Aimed mostly at company systems — you are affected through the companies you use, not your own phone.