CVE-2026-85288 in Notepad++
Summary
by MITRE • 09/22/2026
Notepad++ is a free and open-source source code editor. Prior to 8.9.8, Notepad++ incompletely enforces shortcuts.xml HMAC validation because WM_MACRODLGRUNMACRO, the Run a Macro Multiple Times entry point, calls macroPlayback() without the validation used by command(). A tampered shortcuts.xml macro that is blocked through the Macro menu or a shortcut key can therefore execute through the multi-run dialog and invoke internal Notepad++ commands, including commands that launch external programs, in the current user context. This issue is fixed in version 8.9.8.
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Analysis
by VulDB Data Team • 09/22/2026
Notepad++ is a widely utilized free and open-source source code editor for Microsoft Windows, known for its extensive plugin ecosystem and support for multiple programming languages. The vulnerability described pertains to an incomplete enforcement of security controls within the application's macro execution engine, specifically affecting versions prior to 8.9.8. This flaw arises from an inconsistency in how different entry points validate the integrity of configuration files, creating a bypass mechanism that allows unauthorized code execution under specific conditions.
The technical root cause lies in the disparity between two distinct methods used by Notepad++ to execute macros: the standard command handler and the macro playback function invoked via the multi-run dialog. The shortcuts.xml file contains mappings for keyboard shortcuts and menu commands, including those associated with macros. To prevent tampering, Notepad++ employs Hash-based Message Authentication Codes (HMAC) to verify that these configuration files have not been altered by malicious actors. However, while the standard command() function correctly enforces this HMAC validation before executing a macro, the WM_MACRODLGRUNMACRO entry point, which triggers the macroPlayback() function through the Run a Macro Multiple Times dialog, fails to perform this same integrity check. This oversight creates a critical security gap where an attacker can bypass the intended protection mechanisms by utilizing the multi-run interface rather than standard menu or shortcut invocations.
The operational impact of this vulnerability is significant due to its potential for privilege escalation and arbitrary code execution within the context of the currently logged-in user. An attacker who gains access to the victim's machine, either through physical access, social engineering, or a compromised file system, can craft a malicious shortcuts.xml file containing tampered macro definitions. By directing the victim to use the multi-run dialog feature, the attacker can force Notepad++ to execute these macros without triggering the HMAC validation check. Since internal commands in Notepad++ include functionality that launches external programs, this flaw effectively allows an attacker to run arbitrary executables on the target system. This capability transforms a simple text editor into a vector for executing malware, downloading payloads, or performing other malicious actions with the same privileges as the user running the application.
From a classification perspective, this vulnerability aligns with CWE-20 Improper Input Validation and CWE-862 Missing Authorization, as the software fails to properly validate input data (the shortcuts.xml file) before processing it through an alternative execution path. In terms of adversary tactics, this flaw facilitates ATT&CK technique T1204 User Execution, where a user is tricked into running malicious code, and potentially T1059 Command and Scripting Interpreter if the macro language itself is leveraged for further exploitation. The lack of consistent validation across different UI entry points represents a common architectural weakness in software development known as inconsistent security control enforcement.
To mitigate this risk, organizations relying on Notepad++ must ensure that all instances are updated to version 8.9.8 or later, where the developers have corrected the discrepancy by applying HMAC validation consistently across both standard and multi-run macro execution paths. For environments where immediate patching is not feasible, administrators should restrict user permissions to prevent modification of application configuration files such as shortcuts.xml. Additionally, implementing strict application whitelisting policies can help block unauthorized executables from launching via Notepad++ macros, thereby reducing the blast radius if a vulnerability were to be exploited in unpatched systems. Regular audits of macro configurations and disabling unnecessary features like multi-run execution for non-privileged users are also recommended defensive measures.