16 May 2026
Reference: CVE-2026-42897
1. What is being reported?
The vulnerability involves a weakness in Microsoft Exchange Server's handling of web page content, specifically a type of attack called cross-site scripting (XSS). This means attackers can send specially crafted emails that make it look like they come from a trusted source, potentially fooling users and gaining unauthorised access.
2. What this means in plain English
For a small organisation, this means that if you use Microsoft Exchange Server to manage your emails, attackers could exploit this flaw to impersonate trusted contacts or gain access to sensitive information. This could lead to data breaches or further attacks on your systems.
3. Could this affect a small business?
If your organisation uses Microsoft Exchange Server, especially on-premises versions, you could be at risk. Organisations using cloud-based email services or other email platforms are less likely to be affected. If you are unsure which email system you use, check with your IT provider.
4. What to do now
- Contact your IT provider immediately to check if your Microsoft Exchange Server is affected.
- Apply any security updates or mitigations provided by Microsoft as soon as possible.
- Follow any additional guidance from your IT provider or Microsoft regarding cloud services if applicable.
- If no fix is available, consider discontinuing use of the vulnerable product until it can be secured.
5. Ask your IT provider
Is our Microsoft Exchange Server affected by the CVE-2026-42897 vulnerability, and have all recommended security updates or mitigations been applied?
6. Bottom line
If you use Microsoft Exchange Server, act quickly to secure your email system against this actively exploited vulnerability.
Information based on CISA KEV, NVD and multiple reputable security reports.