A vulnerability in the SNMP code of Cisco Intrusion Prevention System (IPS) Software could allow an unauthenticated, remote attacker to cause the MainApp process to become unresponsive. This creates a denial of service (DoS) condition because the Cisco IPS sensor is not able to execute several critical tasks including alert notification, event store management, and sensor authentication. The Cisco IPS web server will also be unavailable while the MainApp process is unresponsive. Additionally, due to this general system failure, other processes such as the Analysis Engine may not function properly.
The vulnerability is due to improper handling of malformed SNMP packets. An attacker may exploit this vulnerability by sending malformed SNMP packets to the management interface of the affected system. The vulnerability can be triggered by SNMP version 1 (v1), v2, and v3. If the SNMP v3 user is configured with the noAuth option, the attacker could perform the attack without providing valid credentials. Cisco does not recommend configuring the SNMP v3 user with the noAuth option.
Traffic passing through the sensing interfaces will not trigger this vulnerability. If the Cisco IPS is configured in promiscuous mode, mitigation actions that require MainApp processing, such as shun or rate-limit, may be unavailable. If the Cisco IPS is configured in inline mode, the sensor may not correctly perform inspection and mitigation actions because the Analysis Engine process may not be functioning properly.
Cisco has confirmed the vulnerability in a security notice and software updates are available.
To exploit this vulnerability, an attacker may need access to trusted, internal networks to send malformed SNMP packets to the management interface of an affected device. This access requirement may reduce the possibility of a successful exploit.
Cisco indicates that software updates are available for bug ID CSCul49309; however, updates are not available for bug ID CSCum52355.