Advisory ID: cisco-sa-20120926-dhcp
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120926-dhcp
Revision 1.0
For Public Release 2012 September 26 16:00 UTC (GMT)
Contents
Summary
Affected Products
Details
Vulnerability Scoring Details
Impact
Software Versions and Fixes
Workarounds
Obtaining Fixed Software
Exploitation and Public Announcements
Status of This Notice: Final
Distribution
Revision History
Cisco Security Procedures
Summary
Cisco IOS Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition. An attacker could exploit this vulnerability by sending a single DHCP packet to or through an affected device, causing the device to reload.Cisco has released free software updates that address this vulnerability. A workaround that mitigates this vulnerability is available. This advisory is available at the following link:
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120926-dhcp
Note: The September 26, 2012, Cisco IOS Software Security Advisory bundled publication includes nine Cisco Security Advisories. Eight of the advisories address vulnerabilities in Cisco IOS Software, and one advisory addresses a vulnerability in Cisco Unified Communications Manager. Each Cisco IOS Software Security Advisory lists the Cisco IOS Software releases that correct the vulnerability or vulnerabilities detailed in the advisory as well as the Cisco IOS Software releases that correct all Cisco IOS Software vulnerabilities in the September 2012 bundled publication.
Individual publication links are in "Cisco Event Response: Semi-Annual Cisco IOS Software Security Advisory Bundled Publication" at the following link:
http://www.cisco.com/web/about/security/intelligence/Cisco_ERP_sep12.html
Affected Products
Vulnerable Products
To determine whether the Cisco IOS Software release includes the Device Sensor feature, issue the show subsys command.
The following example shows the Device Sensor feature is included:
To determine whether an interface is assigned an IP address, issue the show ip interface brief command.Switch#show subsys | include dsensor_lite dsensor_lite Protocol 1.000.001
The following example indicates the FastEthernet1/0 interface is assigned IP address 10.10.10.1:
router#show ip interface brief Interface IP-Address OK? Method Status Protocol FastEthernet1/0 10.10.10.1 YES manual up up FastEthernet1/1 unassigned YES NVRAM up up
To determine the Cisco IOS Software release that is running on a Cisco product, administrators can log in to the device and issue the show version command to display the system banner. The system banner confirms that the device is running Cisco IOS Software by displaying text similar to "Cisco Internetwork Operating System Software" or "Cisco IOS Software." The image name displays in parentheses, followed by "Version" and the Cisco IOS Software release name. Other Cisco devices do not have the show version command or may provide different output.
The following example identifies a Cisco product that is running Cisco IOS Software Release 15.0(1)M1 with an installed image name of C3900-UNIVERSALK9-M:
Router> show version
Cisco IOS Software, C3900 Software (C3900-UNIVERSALK9-M), Version 15.0(1)M1, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2009 by Cisco Systems, Inc.
Compiled Wed 02-Dec-09 17:17 by prod_rel_team
!--- output truncated
Additional information about Cisco IOS Software release naming conventions is available in "White Paper: Cisco IOS and NX-OS Software Reference Guide" at http://www.cisco.com/web/about/security/intelligence/ios-ref.html.
Products Confirmed Not Vulnerable
No other Cisco products are currently known to be affected by this vulnerability.
Details
Cisco IOS Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a DoS condition. An attacker could exploit this vulnerability by sending a single DHCP packet to or through an affected device, causing the device to reload.
The Device Sensor feature, enabled by default, is vulnerable on devices that have at least one interface with an IP address. The vulnerability is triggered when the Device Sensor feature attempts to process a DHCP packet. In affected releases, valid DHCP packets could trigger this vulnerability.
For more information about the Device Sensor feature, please refer to the Device Sensor Guide.
This vulnerability was previously documented in Cisco bug ID CSCty96049 (registered customers only) and has been assigned the Common Vulnerabilities and Exposures (CVE) ID CVE-2012-4621.
Vulnerability Scoring Details
CVSS is a standards-based scoring method that conveys vulnerability severity and helps organizations determine the urgency and priority of a response.
Cisco has provided a base and temporal score. Customers can also compute environmental scores that help determine the impact of the vulnerability in their own networks.
Cisco has provided additional information regarding CVSS at the following link:
http://www.cisco.com/web/about/security/intelligence/cvss-qandas.html
Cisco has also provided a CVSS calculator to compute the environmental impact for individual networks at the following link:
http://intellishield.cisco.com/security/alertmanager/cvss
|
CSCty96049 - Cisco IOS Software DHCP Server Denial of Service Vulnerability Calculate the environmental score of CSCty96049 |
||||||
|---|---|---|---|---|---|---|
|
CVSS Base Score - 7.8 |
||||||
|
Access Vector |
Access Complexity |
Authentication |
Confidentiality Impact |
Integrity Impact |
Availability Impact |
|
|
Network |
Low |
None |
None |
None |
Complete |
|
|
CVSS Temporal Score - 6.4 |
||||||
|
Exploitability |
Remediation Level |
Report Confidence |
||||
|
Functional |
Official-Fix |
Confirmed |
||||
Impact
Software Versions and Fixes
In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers. Each row of the following Cisco IOS Software table corresponds to a Cisco IOS Software train. If a particular train is vulnerable, the earliest releases that contain the fix are listed in the First Fixed Release column. The First Fixed Release for All Advisories in the September 2012 Bundled Publication column lists the earliest possible releases that correct all the published vulnerabilities in the Cisco IOS Software Security Advisory bundled publication. Cisco recommends upgrading to the latest available release, where possible. The Cisco IOS Software Checker allows customers to search for Cisco Security Advisories that address specific Cisco IOS Software releases. This tool is available on the Cisco Security Intelligence Operations (SIO) portal at http://tools.cisco.com/security/center/selectIOSVersion.x
Cisco IOS Software
| Major Release | Availability of Repaired Releases | |
|---|---|---|
| Affected 12.0-Based Releases | First Fixed Release | First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication |
| There are no affected 12.0 based releases | ||
| Affected 12.2-Based Releases | First Fixed Release | First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication |
| There are no affected 12.2 based releases | ||
| Affected 12.3-Based Releases | First Fixed Release | First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication |
| There are no affected 12.3 based releases | ||
| Affected 12.4-Based Releases | First Fixed Release | First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication |
| There are no affected 12.4 based releases | ||
| Affected 15.0-Based Releases | First Fixed Release | First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication |
| 15.0EX | Not vulnerable |
Not vulnerable |
| 15.0EY | Not vulnerable |
Not vulnerable |
| 15.0M | Not vulnerable |
15.0(1)M9 |
| 15.0MR | Not vulnerable |
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory. |
| 15.0MRA | Not vulnerable |
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory. |
| 15.0S | Not vulnerable Cisco IOS XE devices: Please see Cisco IOS XE Software Availability |
15.0(1)S6 Cisco IOS XE devices: Please see Cisco IOS XE Software Availability |
| 15.0SE | 15.0(1)SE3 15.0(2)SE 15.0(2)SE1; Available on 10-DEC-12 |
15.0(2)SE |
| 15.0SG | Not vulnerable Cisco IOS XE devices: Please see Cisco IOS XE Software Availability |
15.0(2)SG5 15.0(2)SG6 ; Available on 11-OCT-12 Cisco IOS XE devices: Please see Cisco IOS XE Software Availability |
| 15.0SY | Not vulnerable |
15.0(1)SY2 |
| 15.0XA | Not vulnerable |
Vulnerable; First fixed in Release 15.1M |
| 15.0XO | Cisco IOS XE devices: Please see Cisco IOS-XE Software Availability |
Cisco IOS XE devices: Please see Cisco IOS-XE Software Availability |
| Affected 15.1-Based Releases | First Fixed Release | First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication |
| 15.1EY | Not vulnerable |
15.1(2)EY4 |
| 15.1GC | Not vulnerable |
Vulnerable; First fixed in Release 15.1M |
| 15.1M | Not vulnerable |
15.1(4)M5 |
| 15.1MR | Not vulnerable |
15.1(3)MR; Available on 01-OCT-12 |
| 15.1S | Not vulnerable Cisco IOS XE devices: Please see Cisco IOS XE Software Availability |
15.1(3)S Cisco IOS XE devices: Please see Cisco IOS XE Software Availability |
| 15.1SG | 15.1(1)SG1 15.1(2)SG; Available on 12-NOV-12 Cisco IOS XE devices: Please see Cisco IOS XE Software Availability |
15.1(1)SG1 15.1(2)SG 12-NOV-12 Cisco IOS XE devices: Please see Cisco IOS XE Software Availability |
| 15.1SNG | Not vulnerable |
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory. |
| 15.1SNH | Not vulnerable |
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory. |
| 15.1SNI | Not vulnerable |
Vulnerable; migrate to any release in 15.2SNG |
| 15.1SV | Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory. |
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory. |
| 15.1T | Not vulnerable |
Vulnerable; First fixed in Release 15.1M |
| 15.1XB | Not vulnerable |
Vulnerable; First fixed in Release 15.1M |
| Affected 15.2-Based Releases | First Fixed Release | First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication |
| 15.2GC | Not vulnerable |
Releases prior to 15.2(3)GC are vulnerable; Releases 15.2(3)GC and later are not vulnerable. First fixed in Release 15.2T |
| 15.2JA | Not vulnerable |
Not Vulnerable |
| 15.2M | Not vulnerable |
Not vulnerable |
| 15.2S | 15.2(2)S1 Cisco IOS XE devices: Please see Cisco IOS XE Software Availability |
15.2(1)S2 15.2(2)S1 15.2(4)S Cisco IOS XE devices: Please see Cisco IOS XE Software Availability |
| 15.2SNG | Not vulnerable |
Not vulnerable |
| 15.2T | Not vulnerable |
15.2(1)T3 15.2(2)T2 15.2(3)T2; Available on 12-OCT-12 |
Cisco IOS XE Software
Cisco IOS XE Software is not affected by this vulnerability.
Cisco IOS XR Software
Workarounds
In the following example, the global configuration command is issued:
Switch# configure terminal Switch(config)# device-sensor filter-spec dhcp exclude all
To confirm that the Device Sensor feature is no longer collecting DHCP data, issue the show device-sensor cache all command. No DHCP entries should be present in the table.
In the following example, the following table contains only Cisco Discover Protocol data:
Switch# show device-sensor cache all Device: 000f.f7a7.234f on port GigabitEthernet2/1 -------------------------------------------------- Proto Type:Name Len Value cdp 22:mgmt-address-type 8 00 16 00 08 00 00 00 00 cdp 19:cos-type 5 00 13 00 05 00 cdp 18:trust-type 5 00 12 00 05 00 cdp 11:duplex-type 5 00 0B 00 05 01 cdp 10:native-vlan-type 6 00 0A 00 06 00 01 cdp 9:vtp-mgmt-domain-type 9 00 09 00 09 63 69 73 63 6F
Obtaining Fixed Software
Customers may only install and expect support for feature sets they have purchased. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of the Cisco software license at http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.html.
Customers with Service Contracts
Customers Using Third-Party Support Organizations
The effectiveness of any workaround or fix depends on specific customer situations, such as product mix, network topology, traffic behavior, and organizational mission. Because of the variety of affected products and releases, customers should consult their service providers or support organizations to ensure that any applied workaround or fix is the most appropriate in the intended network before it is deployed.
Customers Without Service Contracts
- +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
Customers should have the product serial number available and be prepared to provide the URL of this advisory as evidence of entitlement to a free upgrade. Customers without service contracts should request free upgrades through the TAC.
Refer to Cisco Worldwide Contacts at http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html for additional TAC contact information, including localized telephone numbers, instructions, and e-mail addresses for support in various languages.
Exploitation and Public Announcements
This vulnerability was found during the troubleshooting of customer service requests.
Status of This Notice: Final
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.
Distribution
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120926-dhcp
Additionally, a text version of this advisory is clear signed with the Cisco PSIRT PGP key and circulated among the following e-mail addresses:
- cust-security-announce@cisco.com
- first-bulletins@lists.first.org
- bugtraq@securityfocus.com
- vulnwatch@vulnwatch.org
- cisco@spot.colorado.edu
- cisco-nsp@puck.nether.net
- full-disclosure@lists.grok.org.uk
Future updates of this advisory, if any, will reside on Cisco.com but may not be announced on mailing lists. Users can monitor this advisory's URL for any updates.
Revision History
| Revision 1.0 | 2012-September-26 | Initial public release. |
