Microsoft has recently addressed a significant security vulnerability in the Windows Notepad application, which previously allowed attackers to execute code remotely on targeted systems. Known as CVE-2026-20841, this remote code execution (RCE) flaw was identified with a CVSS v3.1 base score of 8.8 out of 10, indicating its critical nature.
Details of the Vulnerability
The flaw was disclosed during the Microsoft Patch Tuesday updates on February 10, 2026. It arises from improper neutralization of special elements used in commands, a condition referred to as Command Injection (CWE-77). This flaw impacts the Windows Notepad app accessible through the Microsoft Store.
Hackers could exploit this vulnerability by persuading users to open compromised Markdown (.md) files, which contain malicious links. These links, when clicked, instigate Notepad to process unverified protocols, leading the app to download and execute harmful files.
Potential Impact and Exploitation
The exploitation of this vulnerability involves attackers embedding hyperlinks with custom schemes in Markdown files. These links may appear benign but actually direct to attacker-controlled servers. If a user clicks such a link in Notepad, it can result in command injection, allowing the execution of arbitrary commands under the user’s security privileges.
The severity is heightened if the user holds administrative rights, as attackers could then access sensitive files or escalate their privileges further, posing significant security risks.
Mitigation and Recommendations
To mitigate this risk, Microsoft has issued a patch for the Notepad app (build 11.2510+), available via the Microsoft Store. Users are advised to update their applications either manually or by enabling automatic updates in their Windows settings.
Additionally, users should exercise caution by avoiding opening Markdown files from unknown sources and refraining from clicking links within these files. Employing antivirus software with behavior-based detection can also help identify and prevent any suspicious protocol handling activities.
Microsoft acknowledges the contributions of independent researchers Delta Obscura and “chen” for their role in disclosing this vulnerability. This incident highlights the increasing complexity and risks associated with everyday applications like Notepad, which have evolved beyond simple text editing tools.
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