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AUSCERT External Security Bulletin Redistribution
ESB-2015.0771
Cisco IOS XR Software DHCPv4 Server Denial of Service Vulnerability
30 March 2015
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AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco ASR 9000 Series
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2015-0672
Original Bulletin:
http://tools.cisco.com/security/center/viewAlert.x?alertId=38006
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Vulnerability Alert
Cisco IOS XR Software DHCPv4 Server Denial of Service Vulnerability
Threat Type: CWE-399: Resource Management Errors
IntelliShield ID: 38006
Version: 1
First Published: 2015 March 24 17:17 GMT
Last Published: 2015 March 24 17:17 GMT
Port: Not available
CVE: CVE-2015-0672
Urgency: Unlikely Use
Credibility: Confirmed
Severity: Mild Damage
CVSS Base: 5.0 CVSS Calculator
CVSS Version 2.0
CVSS Temporal: 4.1
Version Summary: Cisco IOS XR Software for Cisco ASR 9000 Series Aggregation
Services Routers contains a vulnerability that could allow an unauthenticated,
remote attacker to cause a denial of service condition. Updates are available.
Description
A vulnerability in the DHCP process of Cisco IOS XR Software for Cisco ASR
9000 Series Aggregation Services Routers could allow an unauthenticated,
remote attacker to cause a denial of service (DoS) condition.
The vulnerability is due to improper processing of crafted DHCP messages on a
targeted interface of an affected device. An unauthenticated, remote attacker
could exploit this vulnerability by sending large amounts of crafted DHCP
messages to a targeted interface on an affected device. A successful exploit
could cause the device to stop responding to DHCP requests on that interface,
resulting in a DoS condition.
Cisco has confirmed the vulnerability and released software updates.
Warning Indicators
At the time this alert was first published, Cisco IOS XR Software for Cisco
ASR 9000 Series Aggregation Services Routers version 5.2.2 was vulnerable.
Later versions of Cisco IOS XR Software for Cisco ASR 9000 Series Aggregation
Services Routers may also be vulnerable.
IntelliShield Analysis
To exploit this vulnerability, an attacker may need access to trusted,
internal networks behind a firewall to send large amounts of crafted DHCP
messages to an interface on the device. This access requirement may reduce the
likelihood of a successful exploit.
Cisco indicates through the CVSS score that functional exploit code exists;
however, the code is not known to be publicly available.
Vendor Announcements
Cisco has released bug ID CSCup67822 for registered users that contains
additional details and an up-to-date list of affected product versions.
Impact
An unauthenticated, remote attacker could exploit this vulnerability to cause
a targeted interface on an affected device to stop responding to DHCP
requests, resulting in a DoS condition.
Technical Information
The vulnerability is due to improper processing of crafted DHCP messages on a
particular interface of an affected device.
An unauthenticated, remote attacker could exploit this vulnerability by
sending large amounts of crafted DHCP messages to a targeted interface on an
affected device. A successful exploit could cause the device to stop
responding to DHCP requests on that interface, resulting in a DoS condition.
Safeguards
Administrators are advised to apply the appropriate updates.
Administrators are advised to allow only trusted users to have network access.
Administrators may consider using IP-based access control lists (ACLs) to
allow only trusted systems to access the affected systems.
Administrators can help protect affected systems from external attacks by
using a solid firewall strategy.
Administrators are advised to monitor affected systems.
Patches/Software
Cisco customers with active contracts should contact their Cisco support team
for assistance in upgrading to a software version that includes fixes for this
vulnerability. Cisco customers without contracts may contact the Cisco
Technical Assistance Center at 1-800-553-2447 or 1-408-526-7209 or via email
at tac@cisco.com for assistance.
Alert History
Initial Release
Product Sets
The security vulnerability applies to the following combinations of products.
Primary Products:
Cisco Cisco ASR 9000 Series Aggregation Services Routers 5.2.2 Base
Associated Products:
N/A
Alerts and bulletins on the Cisco Security Intelligence Operations Portal are
highlighted by analysts in the Cisco Threat Operations Center and represent a
subset of the comprehensive content that is available through Cisco Security
IntelliShield Alert Manager Service. This customizable threat and
vulnerability alert service provides security staff with access to timely,
accurate, and credible information about threats and vulnerabilities that may
affect their environment.
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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