CVE-2015-0617 in ASR 5500
Summary
by MITRE
Cisco ASR 5500 System Architecture Evolution (SAE) Gateway devices allow remote attackers to cause a denial of service (CPU consumption and SNMP outage) via malformed SNMP packets, aka Bug ID CSCur13393.
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Analysis
by VulDB Data Team • 07/10/2017
The vulnerability identified as CVE-2015-0617 affects Cisco ASR 5500 System Architecture Evolution gateways, which are critical components in telecommunications infrastructure serving as core routers and gateways for service provider networks. These devices operate as part of the Service Provider Edge architecture and are responsible for handling various network protocols including SNMP for network management and monitoring purposes. The flaw resides in the SNMP processing functionality of these systems, specifically in how they handle malformed SNMP packets that are sent from remote locations without requiring authentication or authorization. This vulnerability represents a significant security concern as it allows unauthenticated remote attackers to exploit the device's SNMP implementation, leading to service disruption and potential network outages that can impact large-scale telecommunications operations.
The technical implementation of this vulnerability stems from insufficient input validation within the SNMP processing module of the Cisco ASR 5500 SAE gateway. When the device receives malformed SNMP packets, the system fails to properly validate the packet structure and content before processing them, leading to a condition where the device enters an infinite loop or consumes excessive CPU resources during packet parsing. This improper handling of malformed input causes the device to allocate resources inefficiently, resulting in CPU utilization spikes that can reach 100% and render the device unable to process legitimate network traffic. The SNMP service becomes unresponsive and eventually goes offline, creating a complete denial of service condition that affects network management capabilities and overall device functionality. The vulnerability specifically affects the SNMPv1 and SNMPv2c implementations within the affected Cisco devices, making it particularly dangerous given the widespread use of these protocols in network management operations.
The operational impact of this vulnerability extends beyond simple service disruption to encompass broader network reliability and availability concerns for service providers and enterprises relying on Cisco ASR 5500 systems. Network administrators may experience complete loss of SNMP monitoring capabilities, which can prevent them from detecting and responding to other network issues, creating a cascading effect that impacts overall network management. The CPU exhaustion caused by the vulnerability can lead to device instability and potential system crashes, requiring manual intervention to restore normal operations through device rebooting. Organizations may face significant downtime during attack windows, particularly during peak network usage periods, resulting in service degradation for end customers. The vulnerability also creates challenges for network security operations centers that depend on SNMP for real-time monitoring and alerting, as the service outage prevents them from receiving critical network status information. This type of denial of service attack can be particularly damaging in mission-critical network environments where continuous availability is essential for business operations.
Cisco has released security advisories and patches to address this vulnerability, recommending immediate deployment of software updates that include enhanced input validation for SNMP packets. Network administrators should implement network segmentation and access control measures to limit exposure by restricting SNMP traffic to trusted management networks only, though this approach provides only partial protection. The vulnerability aligns with CWE-129, which describes improper validation of input boundaries, and represents a classic example of a resource exhaustion attack that can be classified under ATT&CK technique T1499.004 for network denial of service. Organizations should also consider implementing intrusion detection systems that can identify and alert on malformed SNMP traffic patterns, and establish monitoring procedures to detect unusual CPU utilization spikes that may indicate exploitation attempts. The patching process requires careful planning and testing to ensure that updated firmware does not introduce compatibility issues with existing network configurations or services, particularly in complex multi-vendor environments where the ASR 5500 devices interact with other network infrastructure components.