Detection Guidance

This vulnerability arises when Notepad++ launches Windows Explorer without an absolute executable path, allowing execution of a malicious explorer.exe if an attacker controls the process working directory.

To detect this vulnerability on your system, you can check the version of Notepad++ installed to see if it is prior to 8.9.2, as versions before this are vulnerable.

Additionally, you can inspect the working directories from which Notepad++ is launched and verify if any untrusted directories contain an explorer.exe file that could be malicious.

Suggested commands to help detect potential exploitation or presence of malicious explorer.exe include:

• Check Notepad++ version: run `notepad++ --version` or check the About dialog in the application.
• Search for explorer.exe files in directories that might be in the working directory path or user-controlled paths: `dir /s /b explorer.exe` from command prompt in relevant directories.
• Monitor process creation events to detect if explorer.exe is launched from unexpected locations using tools like Sysinternals Process Monitor or Windows Event Logs.
• Use PowerShell to check the path of running explorer.exe processes: `Get-Process explorer | Select-Object Path`.

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Mitigation Strategies

[{'type': 'paragraph', 'content': 'The primary mitigation step is to update Notepad++ to version 8.9.2 or later, where this vulnerability has been patched.'}, {'type': 'paragraph', 'content': 'Until the update is applied, avoid launching Notepad++ from directories that could be controlled by untrusted users or processes to prevent malicious explorer.exe execution.'}, {'type': 'paragraph', 'content': 'Ensure that no malicious explorer.exe files exist in directories that could be searched before the legitimate system directories.'}, {'type': 'paragraph', 'content': "Consider restricting user permissions to prevent placing executables in directories that could influence Notepad++'s working directory."}, {'type': 'paragraph', 'content': 'If possible, disable or limit the use of the auto-updater until the patched version is installed, or deploy the MSI package with the NOUPDATER=1 flag to prevent update-related risks.'}] [1, 3]

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Executive Summary

[{'type': 'paragraph', 'content': 'CVE-2026-25926 is an Untrusted Search Path vulnerability (CWE-426) in Notepad++ versions prior to 8.9.2. The issue occurs when Notepad++ launches Windows Explorer without specifying the absolute path to the executable. Because Windows resolves executables by searching directories in a specific order, including the current working directory before trusted system locations, an attacker who controls the working directory can place a malicious "explorer.exe" that will be executed instead of the legitimate Windows Explorer.'}, {'type': 'paragraph', 'content': 'This vulnerability can lead to arbitrary code execution within the context of the running Notepad++ application, potentially allowing an attacker to run malicious code with the privileges of Notepad++. The malicious executable can mimic expected behavior to avoid detection while executing harmful actions.'}] [1]

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Impact Analysis

This vulnerability can allow an attacker to execute arbitrary code on your system with the privileges of the Notepad++ application. If exploited, it could lead to system compromise, including unauthorized access, data modification, or disruption of services.

• Execution of malicious code disguised as Windows Explorer.
• Potential full compromise of the system depending on Notepad++ privileges.
• Loss of confidentiality, integrity, and availability of data and system resources.

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Compliance Impact

I don't know

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