Cisco IOS Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service condition. Updates are available.
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.
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.
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.
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.
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.
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 email@example.com.
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