CERT-In flags security vulnerabilities in Microsoft Office app

Since its launch in June 1989, the Microsoft Office app continues to be the most popular productivity tool on all platforms, including iOS, Android and Windows worldwide. It has been subscribed to by more than 3.7 million global companies with a 1.2 billion-plus active user base.

Given the fact that billions of people use Microsoft Office, it also attracts cyber criminals try ingenious tricks to breach the application and steal users' personal and financial information. While users are advised to be cautious while on the internet, it is also the job of service providers to have strong security against threat actors. But sometimes, due to unintentional oversight by the engineer, leave security loopholes in application.

In the latest instance, a vulnerability (CVE-2026-45659) with a high severity rating has been detected in Microsoft Office. If this is not fixed, there is a high risk of remote code execution, unauthorised access and potential system compromise, noted the Indian Computer Emergency Response Team (CERT-In).

The issue is due to deserialisation of untrusted data in the Microsoft Office app. In layman's terms, when an unsuspecting user tries to use the Microsoft Office app to open a document file laced with malware, the app's security fails to recognise the threat in the file and the malware slips into the computer, allowing threat actors to steal personal information in the targeted system.

Microsoft Office app now available on Google Play for Android phones

Microsoft has acknowledged the issue and has released the update to the Office app. Users are advised to update their app to the latest version.

In a related development, recently CERT-In flagged similar cyber threats in Microsoft 365 Copilot.

CERT-In noted that Microsoft's product has issues with input validation, there is an authentication weakness, authorisation issues and command handling flaws.

If the issue is not resolved soon, it can allow attackers to execute arbitrary code, steal sensitive information, cause denial of service on affected systems, and there is a high risk of disruption of cloud services.

Here's how to update your Microsoft Office apps:

Step 1: Open the Microsoft Office Word app

Step 2: Click File in the top-left corner, then select Account (or Office Account) from the menu.

Step 3: Under the Product Information section, click Update Options.

Step 4: Select Update Now. (If you don't see this, click Enable Updates first).

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