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 an vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition.
The vulnerability exists in the Network Time Protocol (NTP) component of the affected systems. On systems that support NTP version 4, an unauthenticated, remote attacker could send a crafted NTP packet to the affected system. This action could cause the system to reload, resulting in a DoS condition. Repeated attacks could result in a persistent 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
Only systems that support NTP version 4 are affected. More details on determining if a system is affected can be found in the vendor advisory.
Because the attack can be staged on a UDP port, an attacker could bypass IP-based ACLs by using a spoofed IP address.
The attack does not require any authentication, and devices that are configured with NTP peer authentication are still vulnerable.
Cisco indicates through the CVSS score that functional exploit code exists; however, the code is not known to be publicly available.
An unauthenticated, remote attacker could exploit this vulnerability to cause the affected device to reload, resulting in a DoS condition.
Technical Information
The vulnerability exists in the NTP component of the affected device. When the device has enabled NTP version 4, an unauthenticated, remote attacker could send a crafted NTP packet to UDP port 123. When the affected device attempts to create a reply packet, the device could reload, resulting in a DoS condition.
Safeguards
Administrators are advised to apply the appropriate updates.
Administrators may consider disabling NTP.
Administrators may consider using only broadcast-based association on affected systems.
Administrators may considering enabling Unicast Reverse Path Forwarding (Unicast RPF) and implement IP-based access control lists (ACLs) to restrict access to UDP port 123 to trusted systems. Unicast RPF can help prevent IP spoofing as a bypass of IP-based ACLs.
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.
The security vulnerability applies to the following combinations of products.
Primary Products:
Cisco
IOS
12.2XNA Base | 12.2XNB Base | 12.2XNC Base | 12.2XND Base | 12.4MD Base | 12.4T Base | 12.4XZ Base | 12.4YA Base | 12.4YD Base | 12.4YE 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. Cisco is pleased to offer a free trial of the service.
To register for full access, please visit the IntelliShield trial registration page.
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.
