Microsoft Office: code execution flaw under attack

What is affected

Microsoft Office is found on ordinary personal computers and phones, so this is not only a problem for companies. If you use it and have not updated since the fix was released, you are exposed.

Microsoft Office PowerPoint contains a code injection vulnerability that allows remote attackers to execute arbitrary code via a PowerPoint file with an OutlineTextRefAtom containing an invalid index value that triggers memory corruption.

What an attacker can do

This is a code execution flaw. It lets an attacker run their own commands or programs on the affected system. In practice that usually means taking it over: installing malware, stealing data or using it to reach other devices on the same network.

How it is reached

Over the internet or network

Access the attacker needs

No account needed

Does the victim have to do something?

Yes, the victim must open or click something

What to do

1. Update Microsoft Office now. Open the update or "About" screen, install whatever is offered and restart the app or device, because the fix is not active until you do.
2. Turn on automatic updates so the next fix arrives without you having to look for it.
3. If your device is too old to receive this update, stop using the affected app for anything sensitive and plan a replacement.

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Vendor advisories and fixes

• learn.microsoft.comlearn.microsoft.com/en-us/security-updates/securitybulletins/2009/ms09-017

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on January 7, 2026, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by January 28, 2026, a deadline that has already passed. That deadline does not bind anyone else, but it shows how seriously the agency rates it.

The EPSS model estimates a 67% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 99.3% of all scored vulnerabilities.

Its CVSS severity score is 8.8 out of 10 (high), as recorded in the US National Vulnerability Database.

Technical description

Microsoft Office PowerPoint 2000 SP3, 2002 SP3, and 2003 SP3, and PowerPoint in Microsoft Office 2004 for Mac, allows remote attackers to execute arbitrary code via a PowerPoint file with an OutlineTextRefAtom containing an an invalid index value that triggers memory corruption, as exploited in the wild in April 2009 by Exploit:Win32/Apptom.gen, aka "Memory Corruption Vulnerability."