Advisory ID: cisco-sa-20060112-wirelessRevision 1.0
For Public Release 2006 January 12 16:00 UTC (GMT)
A vulnerability exists in Cisco Aironet Wireless Access Points (AP)
running IOS which may allow a malicious user to send a crafted attack via IP
address Resolution Protocol (ARP) to the Access point which will cause the
device to stop passing traffic and/or drop user connections.
Repeated exploitation of this vulnerability will create a sustained
DoS (denial of service).
Cisco has made free software available to address this vulnerability
for affected customers. There are workarounds available to mitigate the effects
of the vulnerability.
This advisory is posted at
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20060112-wireless.
This section provides details on affected products.
This security advisory applies to all Cisco Aironet Wireless Access
Points that run Cisco IOS Software. The affected device types include:
-
Cisco Aironet 1400 Series Wireless Bridges
-
Cisco Aironet 1300 Series Access Points
-
Cisco Aironet 1240AG Series Access Points
-
Cisco Aironet 1230AG Series Access Points
-
Cisco Aironet 1200 Series Access Points
-
Cisco Aironet 1130AG Series Access Points
-
Cisco Aironet 1100 Series Access Points
-
Cisco Aironet 350 Series Access Points running IOS
Cisco Wireless devices running a VxWorks based image (Version 12.05
and earlier)
No other Cisco products are currently known to be affected by this
vulnerability.
The Address Resolution Protocol (ARP) is used to dynamically map
physical hardware addresses to an IP address. Network devices and workstations
maintain internal tables in which these mappings are stored for some period of
time.
An attacker, who has successfully associated with a Cisco IOS Wireless
Access Point, may be able to spoof ARP messages to the management interface on
the Access Point. The attacker could add entries to the ARP table on the device
until physical memory has been completely exhausted. This will leave the device
in a state where it is unable to pass traffic until the device has been
reloaded by cycling the power.
After upgrading the Access Point (see Software Versions and Fixes), add
the command L2-FILTER BLOCK-ARP to each radio interface.
EXAMPLE:
!
!
interface Dot11Radio0
l2-filter block-arp
!
!
This vulnerability is documented in the Cisco Bug Toolkit as Bug ID
CSCsc16644
(
registered customers only)
Successful exploitation of this vulnerability may result in a denial of
service (DoS) impacting the availability of the Wireless Access Point.
Management and packet forwarding services will be unavailable.
This issue is fixed in IOS version 12.3-7-JA2 which is available for
download at
http://tools.cisco.com/support/downloads/pub/Redirect.x?mdfid=278875243.
It is important to note that in addition to the software upgrade, a
configuration change is also necessary to resolve this vulnerability. Please
see the Details section for information on this configuration change.
When considering software upgrades, also consult
http://www.cisco.com/go/psirt
and any subsequent advisories to determine exposure and a complete upgrade
solution.
In all cases, customers should exercise caution to be certain the
devices to be upgraded contain sufficient memory and that current hardware and
software configurations will continue to be supported properly by the new
release. If the information is not clear, contact the Cisco Technical
Assistance Center ("TAC") or your contracted maintenance provider for
assistance.
The workaround for this issue is to use Virtual LANs (VLANs) to
isolate wireless clients from the Access Point (AP) management interface. A
wireless VLAN infrastructure can be deployed that places AP management
interfaces in one VLAN and places wireless clients into different VLANs based
on SSID. No wireless clients should be allowed on the same VLAN as the
management interface of the AP. There are several design considerations that
must be accounted for when deploying VLANs on the wireless network. For a
discussion of the prerequisites, design considerations, and wireless and wired
hardware configuration examples refer to:
Using VLANs with Cisco Aironet Wireless Equipment
http://www.cisco.com/en/US/products/hw/wireless/ps4570/products_configuration_example09186a00801d0815.shtml
Additional information is available at:
Configuring VLANs
http://www.cisco.com/en/US/docs/wireless/access_point/12.3_2_JA/configuration/guide/s32vlan.html
In this example an existing AP is reconfigured to use VLANs. The AP is
configured in VLAN 10 (the native VLAN) and wireless clients are configured in
VLANS 20 and 30.
Creating VLANs will disable existing SSIDs. So for this example, the
existing SSID was deleted, the VLANs were created, Encryption Mode and Keys
were then set for each VLAN, and SSIDs were created for each VLAN.
!
! Set encryption ciphers and broadcast key rotation
!
interface Dot11Radio0
no ip address
no ip route-cache
!
encryption mode ciphers tkip
!
encryption vlan 10 mode ciphers tkip
! Encryption ciphers are set under the physical radio interface
!
encryption vlan 20 mode ciphers tkip
!
encryption vlan 30 mode ciphers tkip
!
broadcast-key change 43000
!
broadcast-key vlan 10 change 43000
! Broadcast key rotation is set under the physical radio interface
!
broadcast-key vlan 20 change 43000
!
broadcast-key vlan 30 change 43000
!
!
!
! Set the SSID's and their vlans and authentication method
!
ssid ap-devices-only
! each SSID must have a vlan and authentication settings
vlan 10
authentication open eap eap_methods
authentication network-eap eap_methods
authentication key-management wpa
!
ssid red20
vlan 20
authentication open eap eap_methods
authentication network-eap eap_methods
authentication key-management wpa
!
ssid red30
vlan 30
authentication open eap eap_methods
authentication network-eap eap_methods
authentication key-management wpa
!--------------------------
! Consider not configuring an SSID for the native VLAN
! which in this example is VLAN 10. Not configuring an
! SSID for the native VLAN will prevent all wireless
! clients from estabishing management connections to
! the AP
!-------------------------
!
interface Dot11Radio0.10
encapsulation dot1Q 10 native
! AP's are placed in this VLAN
no ip proxy-arp
no ip route-cache
no cdp enable
bridge-group 1
bridge-group 1 spanning-disabled
! If the virtual interfaces are configured via the HTTP GUI
! the bridge-group settings will be configured automatically
!
interface Dot11Radio0.20
encapsulation dot1Q 20
! Clients are placed in this VLAN
no ip route-cache
no cdp enable
bridge-group 20
bridge-group 20 subscriber-loop-control
bridge-group 20 block-unknown-source
no bridge-group 20 source-learning
no bridge-group 20 unicast-flooding
bridge-group 20 spanning-disabled
!
interface Dot11Radio0.30
encapsulation dot1Q 30
! Clients are placed in this VLAN
no ip route-cache
no cdp enable
bridge-group 30
bridge-group 30 subscriber-loop-control
bridge-group 30 block-unknown-source
no bridge-group 30 source-learning
no bridge-group 30 unicast-flooding
bridge-group 30 spanning-disabled
!
interface FastEthernet0
no ip address
no ip route-cache
duplex auto
speed auto
no cdp enable
!
!
! Set the Wired virtual interfaces
!
interface FastEthernet0.10
encapsulation dot1Q 10 native
no ip proxy-arp
no ip route-cache
no cdp enable
bridge-group 1
no bridge-group 1 source-learning
bridge-group 1 spanning-disabled
! If the virtual interfaces are configured via the HTTP GUI
! the bridge-group settings will be configured automatically
!
interface FastEthernet0.20
encapsulation dot1Q 20
no ip route-cache
no cdp enable
bridge-group 20
no bridge-group 20 source-learning
bridge-group 20 spanning-disabled
!
interface FastEthernet0.30
encapsulation dot1Q 30
no ip route-cache
no cdp enable
bridge-group 30
no bridge-group 30 source-learning
bridge-group 30 spanning-disabled
!
!
! The AP's BVI1 IP address must be from the native VLAN's subnet
!
interface BVI1
ip address 192.168.1.40 255.255.255.0
no ip route-cache
Wireless Network Security Best Practices
In addition to the above workarounds and example, Cisco recommends
deploying Wireless network security best practices which are discussed in the
references below:
SAFE: Wireless LAN Security in Depth - version 2
http://www.cisco.com/en/US/netsol/ns340/ns394/ns171/ns128/networking_solutions_white_paper09186a008009c8b3.shtml
Wireless LAN Security Solution for Large Enterprise
http://www.cisco.com/en/US/netsol/ns340/ns394/ns348/ns386/networking_solutions_package.html
Cisco Wireless LAN Security Overview
http://www.cisco.com/en/US/prod/collateral/wireless/ps5678/ps430/ps4076/prod_brochure09186a00801f7d0b.html
Mitigation
The risk of this issue can be mitigated by requiring all wireless
clients to authenticate with an EAP based authentication protocol such as
EAP-FAST, PEAP, or EAP-TLS. However authenticated users could still exploit
this vulnerability as the mitigation cannot completely eliminate the
vulnerability.
Cisco has made free software available to address this vulnerability
for affected customers. Prior to deploying software, customers should consult
their maintenance provider or check the software for feature set compatibility
and known issues specific to their environment.
Customers may only install and expect support for the feature sets they
have purchased. By installing, downloading, accessing or otherwise using such
software upgrades, customers agree to be bound by the terms of Cisco's software
license terms found at
http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.html,
or as otherwise set forth at Cisco.com Downloads at
http://www.cisco.com/public/sw-center/sw-usingswc.shtml.
Do not contact either "psirt@cisco.com" or "security-alert@cisco.com"
for software upgrades.
Customers with contracts should obtain upgraded software through their
regular update channels. For most customers, this means that upgrades should be
obtained through the Software Center on Cisco's worldwide website at
http://www.cisco.com.
Customers whose Cisco products are provided or maintained through prior
or existing agreement with third-party support organizations such as Cisco
Partners, authorized resellers, or service providers should contact that
support organization for guidance and assistance with the appropriate course of
action in regards to this advisory.
The effectiveness of any workaround or fix is dependent on specific
customer situations such as product mix, network topology, traffic behavior,
and organizational mission. Due to the variety of affected products and
releases, customers should consult with their service provider or support
organization to ensure any applied workaround or fix is the most appropriate
for use in the intended network before it is deployed.
Customers who purchase direct from Cisco but who do not hold a Cisco
service contract and customers who purchase through third-party vendors but are
unsuccessful at obtaining fixed software through their point of sale should get
their upgrades by contacting the Cisco Technical Assistance Center (TAC). TAC
contacts are as follows.
-
+1 800 553 2447 (toll free from within North America)
-
+1 408 526 7209 (toll call from anywhere in the world)
-
e-mail: tac@cisco.com
Have your product serial number available and give the URL of this
notice as evidence of your entitlement to a free upgrade. Free upgrades for
non-contract customers must be requested through the TAC.
Refer to
http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html
for additional TAC contact information, including special localized telephone
numbers and instructions and e-mail addresses for use in various
languages.
The Cisco PSIRT is not aware of any malicious use of the vulnerability
described in this advisory.
This issue was reported to us by Eric Smith at Bucknell
University.
THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.
A stand-alone copy or Paraphrase of the text of this document that omits the distribution URL in the following section is an uncontrolled copy, and may lack important information or contain factual errors.
This advisory is posted on Cisco's worldwide website at
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20060112-wireless.
In addition to worldwide web posting, a text version of this notice is
clear-signed with the Cisco PSIRT PGP key and is posted to the following e-mail
and Usenet news recipients.
-
cust-security-announce@cisco.com
-
first-teams@first.org
-
bugtraq@securityfocus.com
-
vulnwatch@vulnwatch.org
-
cisco@spot.colorado.edu
-
cisco-nsp@puck.nether.net
-
full-disclosure@lists.grok.org.uk
-
comp.dcom.sys.cisco@newsgate.cisco.com
Future updates of this advisory, if any, will be placed on Cisco's
worldwide website, but may or may not be actively announced on mailing lists or
newsgroups. Users concerned about this problem are encouraged to check the
above URL for any updates.
|
Revision 1.0
|
12-January-2006
|
Initial public release
|
|
