Submit #84: uftpd 2.6-2.10 Buffer Overflow

# Buffer Overflow
## Description

There is a buffer overflow vulnerability in `handle_PORT` in `ftpcmd.c` that is caused by a buffer that is 16 bytes large being filled via `sprintf` with user input based on the format specifier string `%d.%d.%d.%d`. The 16 byte size is correct for valid IPv4 addresses (`len('x.x.x.x') == 16`), but the format specifier `%d` allows more than 3 digits.


## Reproduction Steps

To reproduce this vulnerability, connect via `netcat <ip> <port>` and write to the FTP server socket the following and observe the child process spawned for the connection SIGABRT:

```
PORT 13371337,12341234,12345678,10102929,1,2
```


## Mitigation

Use `snprintf` and use the size of the buffer as the size input. Currently, it uses `inet_aton` to validate the IPv4 address, so if the user inputs an invalid address, it will be caught at that line anyway.

• Source: ⚠️ https://aaronesau.com/blog/posts/6
• User: arinerron (UID 4337)
• Submission: 08/31/2019 20:37 (7 years ago)
• Moderation: 09/03/2019 07:11 (2 days later)
• Status: Accepted
• VulDB entry: 141192 [uftpd 2.6-2.10 ftpcmd.c handle_PORT memory corruption]
• Points: 20