Cisco Switches

A Remote Code Execution flaw that affected the Cisco switches that allow an attacker to gain the full control of the Vulnerable Cisco switch deployed networks.

Scanning the entire internet reveal that, 250,000 vulnerable devices have been presented and 8.5 million devices that have a vulnerable port open.

Researchers Found stack-based buffer overflow vulnerability was found in Cisco Switches  Smart Install Client code that allows an attacker to remotely execute arbitrary code without any further authentication.

Smart Install is a Cisco switches new future that provides plug-and-play configuration and image-management.

This Future help to ship a switch to a location, place it in the network and power it on with no configuration on the device required and without an administrator and its also provide a backup configuration.

Also, Director act as common single point manager for images and configuration of client switches and client make both direct and indirect connection to the director.

A discovered critical vulnerability presented in the code of the Cisco Switches Smart Install Client.

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Vulnerability Description in Cisco Switches

According to embedi, The SMI IBC Server Process process contains a Smart Install Client implementation code. The Smart Install Client starts a server on the TCP(4786) port (opened by default) to interact with the Smart Install Director.

In this case, a stack-based buffer overflow occurs when server processing this  ibd_init_discovery_msg specially crafted malicious message and the buffer overflow takes and abuse the function smi_ibc_handle_ibd_init_discovery_msg.

Two Attack Conditions

1.Reset or change the enable password to enter privileged EXEC mode:

2.Intercept traffic between other devices connected to the switch and the Internet:

Check the equipment for vulnerability

Users can check the vulnerability by performing simple network scan using Nmap with Cisco network equipment with an open portTCP 4786.

nmap -p T:4786 192.168.1.0/24

Aslo To check whether the network equipment is of a Smart Install Client type, enter the following commands:

switch>show vstack config
 Role: Client (SmartInstall enabled)
 Vstack Director IP address: 0.0.0.0

switch>show tcp brief all
TCB       Local Address           Foreign Address        (state)
0344B794  *.4786                  *.*                    LISTEN
0350A018  *.443                   *.*                    LISTEN
03293634  *.443                   *.*                    LISTEN
03292D9C  *.80                    *.*                    LISTEN
03292504  *.80                    *.*                    LISTEN

Affected Cisco Switches

  • Catalyst 4500 Supervisor Engines
  • Catalyst 3850 Series
  • Catalyst 3750 Series
  • Catalyst 3650 Series
  • Catalyst 3560 Series
  • Catalyst 2960 Series
  • Catalyst 2975 Series
  • IE 2000
  • IE 3000
  • IE 3010
  • IE 4000
  • IE 4010
  • IE 5000
  • SM-ES2 SKUs
  • SM-ES3 SKUs
  • NME-16ES-1G-P
  • SM-X-ES3 SKUs

This Flaw has been fixed by Cisco and released the patch CVE : CVE-2018-0171