Microsoft Patches High-Severity Remote Code Execution Flaw in Windows Notepad

What happened

Microsoft released a security patch addressing a high-severity remote code execution (RCE) vulnerability in the modern Windows Notepad app, tracked as CVE-2026-20841, that could allow attackers to run malicious code if a user opens a crafted file and clicks a link. 

Who is affected

Endpoints running the Microsoft Store version of Windows Notepad prior to the patched build (11.2510+) are impacted; the classic Notepad.exe isn’t affected, but any enterprise desktops and laptops using the store app remain exposed until updated. 

Why CISOs should care

Although exploitation isn’t widely reported in the wild yet, the flaw scored 8.8 (High) on the CVSS scale and hinges on command injection via malicious Markdown (.md) files — a vector that can bypass traditional trust assumptions about benign apps and user-visible editors. 

3 Practical Actions

1. Deploy the Patch Immediately: Update the Notepad app via the Microsoft Store or enable automatic app updates across endpoints to ensure CVE-2026-20841 is remediated. 
2. Reduce Exposure to Untrusted Files: Implement email and web filtering for untrusted Markdown and other high-risk file types; educate users not to open unexpected attachments or click links in unfamiliar files.
3. Monitor Endpoint Behavior: Leverage EDR/IM tools to detect anomalous Notepad process behavior, especially instances where Notepad spawns external processes or handles unexpected network protocols.