Cisco IOS and IOS XE Software DHCP Remote Code Execution Vulnerability

This vulnerability affects Cisco devices that are running a vulnerable release of Cisco IOS Software or Cisco IOS XE Software and are configured as a DHCP relay agent.

For information about which Cisco IOS and IOS XE Software releases are vulnerable, see the Fixed Software section of this advisory.

Assessing the DHCP Relay Configuration

To determine whether a device is configured as a DHCP relay agent, administrators can log in to the device and use the show running-config | include ip helper-address command in the CLI.

The following example shows the output of the command for a device that is running Cisco IOS Software and is configured as a DHCP relay agent that forwards DHCP packets to the DHCP server address 10.10.10.1:

Router# show running-config | include ip helper-address

ip helper-address  10.10.10.1
Router#

If a device is not configured as a DHCP relay agent, the show running-config | include ip helper-address command will not return any output.

Determining the Cisco IOS Software Release

To determine which Cisco IOS Software release is running on a device, administrators can log in to the device, use the show version command in the CLI, and then refer to the system banner that appears. If the device is running Cisco IOS Software, the system banner displays text similar to Cisco Internetwork Operating System Software or Cisco IOS Software. The banner also displays the installed image name in parentheses, followed by the Cisco IOS Software release number and release name. Some Cisco devices do not support the show version command or may provide different output.

The following example shows the output of the command for a device that is running Cisco IOS Software Release 15.5(2)T1 and has an installed image name of C2951-UNIVERSALK9-M:

Router> show version

Cisco IOS Software, C2951 Software (C2951-UNIVERSALK9-M), Version 15.5(2)T1, RELEASE SOFTWARE (fc1)
Technical Support: http://ift.tt/yGenYU
Copyright (c) 1986-2015 by Cisco Systems, Inc.
Compiled Mon 22-Jun-15 09:32 by prod_rel_team
.
.
.

For information about the naming and numbering conventions for Cisco IOS Software releases, see White Paper: Cisco IOS and NX-OS Software Reference Guide.

Determining the Cisco IOS XE Software Release

To determine which Cisco IOS XE Software release is running on a device, administrators can log in to the device, use the show version command in the CLI, and then refer to the system banner that appears. If the device is running Cisco IOS XE Software, the system banner displays Cisco IOS Software, Cisco IOS XE Software, or similar text.

The following example shows the output of the command for a device that is running Cisco IOS XE Software Release 16.2.1 and has an installed image name of CAT3K_CAA-UNIVERSALK9-M:

ios-xe-device# show version

Cisco IOS Software, Catalyst L3 Switch Software (CAT3K_CAA-UNIVERSALK9-M), Version Denali 16.2.1, RELEASE SOFTWARE (fc1)
Technical Support: http://ift.tt/yGenYU
Copyright (c) 1986-2016 by Cisco Systems, Inc.
Compiled Sun 27-Mar-16 21:47 by mcpre
.
.
.

For information about the naming and numbering conventions for Cisco IOS XE Software releases, see White Paper: Cisco IOS and NX-OS Software Reference Guide.

No other Cisco products are currently known to be affected by this vulnerability.

Cisco has confirmed that this vulnerability does not affect Cisco IOS XR Software or Cisco NX-OS Software.

from Cisco Security Advisory http://ift.tt/2xKcjJb