Vulnerability Alert

Cisco IOS Software DHCP Denial of Service Vulnerability

 
Threat Type:CWE-399: Resource Management Errors
IntelliShield ID:26900
Version:1
First Published:2012 September 26 16:29 GMT
Last Published:2012 September 26 16:29 GMT
Port: Not available
CVE:CVE-2012-4621
Urgency:Unlikely Use
Credibility:Confirmed
Severity:Mild Damage
CVSS Base:7.8 CVSS Calculator
CVSS Version 2.0
CVSS Temporal:6.4
 
Version Summary:Cisco IOS Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service condition. Updates are available.
 
 
Description
Cisco IOS Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on a targeted device.

The vulnerability is due to improper handling of DHCP packets by the Device Sensor feature of Cisco IOS Software. An unauthenticated, remote attacker could exploit this vulnerability by sending a single valid DHCP request to a device that has the Device Sensor feature enabled. A successful exploit could allow the attacker to cause the targeted device to reload, denying service to legitimate users. Sustained attacks could result in a DoS condition.

Cisco has confirmed this vulnerability and released software updates.
 
Warning Indicators
Cisco has published a list of affected Cisco IOS Software releases in the security advisory. The Vendor Announcements section of this alert contains a link to the advisory.
 
IntelliShield Analysis
Cisco devices that are running Cisco IOS Software versions that include the Device Sensor feature and at least one interface configured with an IP address are affected by this vulnerability.

For more information about the Device Sensor feature, refer to the Device Sensor Guide.

Cisco indicates through the CVSS score that functional exploit code exists; however, the code is not known to be publicly available.

To exploit this vulnerability, the attacker may need access to trusted, internal network resources. This access requirement may reduce the likelihood of a successful exploit.

The Device Sensor feature is enabled by default on affected devices. It is possible to mitigate the vulnerability by applying the global configuration command device-sensor filter-spec dhcp exclude all. This command will filter the Device Sensor feature collection of DHCP packets, and the Device Sensor feature will no longer process or store DHCP information. 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.
 
Vendor Announcements
Cisco has released a security advisory for Cisco bug ID CSCty96049 at the following link: cisco-sa-20120926-dhcp
 
Impact
An unauthenticated, remote attacker could exploit this vulnerability causing the targeted device to reload, denying service to legitimate users. Sustained attacks could result in a DoS condition.
 
Technical Information
The vulnerability is due to improper handling of valid DHCP packets by the affected software on devices with the Device Sensor feature enabled. The vulnerability can be triggered by a single valid DHCP packet.

An unauthenticated, remote attacker could exploit this vulnerability by sending a single DHCP request to or through a device that has the Device Sensor feature enabled. When the DHCP packet is processed by the Device Sensor feature, an error condition may occur that the attacker could use to cause the targeted device to reload, denying service to legitimate users. Sustained attacks could result in a DoS condition.
 
Safeguards
Administrators are advised to apply the appropriate updates.

Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected devices.

Administrators are advised to allow only trusted users to have network access.

Administrators are advised to monitor affected systems.

Administrators may consider excluding DHCP packets from collection by the Device Sensor feature by applying the global configuration command device-sensor filter-spec dhcp exclude all.
 
Patches/Software
Cisco customers with active contracts can obtain updates through the Software Center at the following link: Cisco. Cisco customers without contracts can obtain upgrades by contacting the Cisco Technical Assistance Center at 1-800-553-2447 or 1-408-526-7209 or via e-mail at tac@cisco.com.
 
Alert History
 
Initial Release


Product Sets
 
The security vulnerability applies to the following combinations of products.

Primary Products:
CiscoIOS 15.0SE 15.0(1)SE, 15.0(1)SE1, 15.0(1)SE2 | 15.1SG 15.1(1)SG | 15.2S 15.2(2)S, 15.2(2)S0a, 15.2(2)S0c, 15.2(2)S0d

Associated Products:
CiscoIOS 15.2S 15.2(2)S0b




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LEGAL DISCLAIMER
The urgency and severity ratings of this alert are not tailored to individual users; users may value alerts differently based upon their network configurations and circumstances. THE ALERT, AND INFORMATION CONTAINED THEREIN, ARE PROVIDED ON AN "AS IS" BASIS AND DO NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE ALERT, AND INFORMATION CONTAINED THEREIN, OR MATERIALS LINKED FROM THE ALERT, IS AT YOUR OWN RISK. INFORMATION IN THIS ALERT AND ANY RELATED COMMUNICATIONS IS BASED ON OUR KNOWLEDGE AT THE TIME OF PUBLICATION AND IS SUBJECT TO CHANGE WITHOUT NOTICE. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE ALERTS AT ANY TIME.
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