CVE-2026-71858 in Notepad++
Summary
by MITRE • 08/17/2026
Notepad++ is a free and open-source source code editor. Prior to 8.9.7, macros loaded from an attacker-controlled shortcuts.xml bypass the HMAC validation applied to UserDefinedCommands and can invoke Scintilla actions and the internal Open in Default Viewer command in an elevated Notepad++ process, allowing protected file modification and conditional elevated command execution when a local attacker influences settingsDir and a user triggers the macro. This issue is fixed in version 8.9.7.
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Analysis
by VulDB Data Team • 08/17/2026
Notepad++ is a widely used open-source source code editor that supports advanced features such as macros to automate repetitive tasks. A critical security vulnerability was identified in versions prior to 8.9.7, specifically concerning the handling of macro configurations loaded from an attacker-controlled shortcuts.xml file. This flaw allows for the bypassing of Hash-based Message Authentication Code validation mechanisms that are otherwise applied to UserDefinedCommands. The absence of proper integrity checks on these specific configuration elements creates a significant security gap that can be exploited by local attackers under certain conditions.
The technical core of this vulnerability lies in the inconsistent application of cryptographic verification within Notepad++'s macro processing logic. While standard user-defined commands are protected by HMAC validation to ensure they have not been tampered with, macros loaded via the shortcuts.xml file were exempt from these checks. This inconsistency enables an attacker who has access to modify local configuration files or influence the settings directory to inject malicious macro definitions. When a legitimate user subsequently triggers this macro within Notepad++, the application executes the embedded commands without verifying their authenticity or integrity.
The operational impact of this vulnerability is severe due to its potential for privilege escalation and unauthorized file modification. Because macros can invoke Scintilla actions, which are low-level editing operations, an attacker can manipulate text content in protected files if the user has write permissions. More critically, the macro system allows invocation of internal commands such as Open in Default Viewer. If Notepad++ is running with elevated privileges or if the execution context permits it, this mechanism can lead to conditional elevated command execution. This means that a local attacker could potentially execute arbitrary code with higher privileges than their own user account by tricking an administrator or privileged user into opening a maliciously crafted file and triggering the macro.
This vulnerability aligns with CWE-20 Improper Input Validation, as the application fails to adequately validate external input from configuration files before processing it. It also relates to CWE-749 Exposed Dangerous Method in an Unrestricted Context, where powerful internal functions are made accessible through a poorly secured interface. From a threat modeling perspective using MITRE ATT&CK, this scenario reflects techniques associated with Defense Evasion and Privilege Escalation, specifically leveraging trusted applications like Notepad++ to execute malicious payloads or modify system files without detection by standard security controls.
To mitigate the risks associated with this vulnerability, users must upgrade to version 8.9.7 or later of Notepad++, where the HMAC validation has been extended to cover macros loaded from shortcuts.xml as well. Until an update is applied, administrators should restrict file modification permissions on configuration directories such as settingsDir to prevent unauthorized changes by local attackers. Additionally, implementing strict application control policies can help monitor and limit the execution of scripts or macros within Notepad++, reducing the attack surface for exploitation. Regular security audits of user configurations and awareness training regarding macro usage are also recommended practices to enhance overall system resilience against similar configuration-based attacks.