Fix Microsoft 365 Certificate Warning in Kaspersky Antivirus
Question details
The user is encountering a security warning from Kaspersky Antivirus stating that a Microsoft 365 Office application is using an expired certificate to connect to a service.
- Product
- Microsoft 365
- Device & OS
- not provided
- Scenario
- Using Microsoft 365 desktop applications while Kaspersky Antivirus is actively scanning secure network connections.
- Observed behavior
- Kaspersky triggers an expired certificate alert when the Office application attempts to connect to legitimate Microsoft background services, such as omex.cdn.office.net.
Before proceeding, ensure your Kaspersky Antivirus virus definitions are fully updated, as security vendors frequently release patches to recognize newly renewed Microsoft certificates.
Verify the Microsoft Domain and Proceed Safely
Check the URL provided in the Kaspersky warning. If it is a verified Microsoft endpoint, you can safely allow the connection.
Occasionally, background content delivery networks (CDNs) for Microsoft Office experience brief certificate renewal delays. If the domain is officially owned by Microsoft, allowing the connection is generally safe for your daily tasks.
Look closely at the domain name listed in the Kaspersky certificate warning popup (for example, omex.cdn.office.net).
Verify that the address matches Microsoft's published list of official Microsoft 365 URLs and endpoint information.
If the destination is confirmed as a legitimate Microsoft service, click the option in Kaspersky to continue or accept the connection.
If the destination domain looks suspicious or unfamiliar, click 'Disconnect' or 'Block' immediately to protect your system.
Contact Your Administrator or Microsoft Support
If the warning persists over multiple days, escalate the issue to your IT department so they can investigate the network certificate.
Try WPS Office for a Hassle-Free Experience
Tired of dealing with complex Microsoft 365 background connections and antivirus certificate warnings? WPS Office provides a free, lightweight, and highly compatible alternative that works seamlessly offline and online without heavy reliance on background CDN services.
- 1. Visit the website: Go to the official WPS Office website to download the installer.
- 2. Install the software: Run the lightweight installer and follow the on-screen instructions.
- 3. Open your files: Launch WPS Office and instantly open your existing Microsoft Office documents.
Frequently Asked Questions
Why does Kaspersky flag omex.cdn.office.net?
Kaspersky intercepts secure network connections to scan them for threats. If Microsoft is in the middle of renewing a CDN certificate, or if Kaspersky's local database is outdated, the antivirus will temporarily flag the legitimate connection as risky.
Is it safe to ignore the Kaspersky certificate warning for Microsoft 365?
It is generally safe only if you have verified that the domain in the warning strictly belongs to Microsoft (like office.net or microsoft.com). If you are unsure of the URL's origin, do not proceed.
Can I add Microsoft 365 domains to Kaspersky's exclusions?
Yes, you can add trusted Microsoft 365 URLs to Kaspersky's Web Anti-Virus exclusions to prevent these warnings, though keeping the software updated is the preferred and safer method.
