A stack-based buffer overflow vulnerability exists in Notepad++ version 8.9.3 in the file drop handler component. When a user drags and drops a directory path of exactly 259 characters without a trailing backslash, the application appends a backslash and null terminator without proper bounds checking, resulting in a stack buffer overflow and application crash (STATUS_STACK_BUFFER_OVERRUN).

SciLexer.dll in Scintilla in Notepad++ (x64) before 7.7 allows remote code execution or denial of service via Unicode characters in a crafted .ml file.

Notepad++ versions 8.4.1 and before are vulnerable to DLL hijacking where an attacker can replace the vulnerable dll (UxTheme.dll) with his own dll and run arbitrary code in the context of Notepad++.

Notepad++ is a free and open-source source code editor. From 8.9.4 until 8.9.6, Notepad++ contains a local privilege escalation vulnerability in the installer. During installation, the installer invokes powershell.exe without using an absolute path after setting the working directory to the installation contextMenu directory. If an attacker can pre-place a malicious powershell.exe in a user-writable custom installation directory, and a privileged user later runs the installer and selects that directory, the attacker-controlled executable is launched with the elevated privileges of the installer. This vulnerability is fixed in 8.9.6.

Notepad++ is a free and open-source source code editor. Prior to 8.9.6.1, the <GUIConfig name="commandLineInterpreter"> tag in config.xml is read by NppXml::value() (Parameters.cpp:6430) and stored in _nppGUI._commandLineInterpreter without any validation, whitelist, or digital signature check. When the user triggers IDM_FILE_OPEN_CMD (File → Open Containing Folder → cmd), NppCommands.cpp:228 creates a Command object with this value and calls run(), which invokes ShellExecute (RunDlg.cpp:221) with the attacker-controlled string as the executable path. This vulnerability is fixed in 8.9.6.1.

Notepad++ is a free and open-source source code editor. Prior to 8.9.6.1, the <Command> tag text content inside <UserDefinedCommands> in shortcuts.xml is read by NppXml::value(aNode) (Parameters.cpp:3658) in the feedUserCmds() function and stored in UserCommand._cmd without any validation. When the user clicks the corresponding entry in the Run menu, NppCommands.cpp:4264 creates a Command object with string2wstring(ucmd.getCmd()) and calls run(), which invokes ShellExecute (RunDlg.cpp:221) with the attacker-controlled string as the executable path. The injected command appears as a normal menu item in the Run menu, making it a viable persistence mechanism. This vulnerability is fixed in 8.9.6.1.

Notepad++ 7.3.3 (32-bit) with Hex Editor Plugin v0.9.5 might allow user-assisted attackers to execute code via a crafted file, because of a "Data from Faulting Address controls Code Flow" issue. One threat model is a victim who obtains an untrusted crafted file from a remote location and issues several user-defined commands.

Notepad++ is a free and open-source source code editor. Versions 8.5.6 and prior are vulnerable to heap buffer write overflow in `Utf8_16_Read::convert`. This issue may lead to arbitrary code execution. As of time of publication, no known patches are available in existing versions of Notepad++.