CVE-2018-0177 in IOS XE
Summary
by MITRE
A vulnerability in the IP Version 4 (IPv4) processing code of Cisco IOS XE Software running on Cisco Catalyst 3850 and Cisco Catalyst 3650 Series Switches could allow an unauthenticated, remote attacker to cause high CPU utilization, traceback messages, or a reload of an affected device that leads to a denial of service (DoS) condition. The vulnerability is due to incorrect processing of certain IPv4 packets. An attacker could exploit this vulnerability by sending specific IPv4 packets to an IPv4 address on an affected device. A successful exploit could allow the attacker to cause high CPU utilization, traceback messages, or a reload of the affected device that leads to a DoS condition. If the switch does not reboot when under attack, it would require manual intervention to reload the device. This vulnerability affects Cisco Catalyst 3850 and Cisco Catalyst 3650 Series Switches that are running Cisco IOS XE Software Release 16.1.1 or later, until the first fixed release, and are configured with an IPv4 address. Cisco Bug IDs: CSCvd80714.
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Analysis
by VulDB Data Team • 02/06/2021
This vulnerability resides within the IPv4 processing implementation of Cisco IOS XE Software affecting Catalyst 3850 and 3650 Series switches operating on software releases 16.1.1 and later. The flaw manifests as improper handling of specific IPv4 packets that triggers abnormal CPU resource consumption patterns and system instability. The vulnerability represents a classic denial of service condition where an attacker can manipulate network traffic to exhaust system resources without requiring authentication credentials, making it particularly dangerous in network environments where unauthorized access is a concern. The affected devices maintain their operational state during the attack but experience significant performance degradation that ultimately leads to service disruption.
The technical root cause stems from inadequate validation and processing logic within the IPv4 packet handling routines of the IOS XE operating system. When malformed or specially crafted IPv4 packets are received by an affected switch, the processing code fails to properly handle the packet structures, causing the CPU to consume excessive resources in attempting to process these anomalous packets. This improper packet handling can result in system traceback messages indicating internal processing errors and may ultimately force the device to reload automatically, or require manual intervention to restore normal operations. The vulnerability specifically targets the IPv4 address processing functionality, making it distinct from other network protocol vulnerabilities that might affect different layers of the network stack.
From an operational impact perspective, this vulnerability creates significant risk for network availability and reliability in enterprise environments where these switches serve as critical network infrastructure components. The DoS condition can disrupt network connectivity for extended periods while administrators must either wait for automatic recovery or manually intervene to restart affected devices. Network administrators face the challenge of identifying and mitigating the attack without disrupting legitimate network traffic, as the malicious packets appear to be valid IPv4 traffic. The vulnerability affects network performance metrics and can potentially impact business operations depending on the criticality of the affected network segments.
Mitigation strategies for this vulnerability should include immediate implementation of access control measures such as applying ACLs to filter incoming IPv4 traffic, particularly targeting known attack patterns and source addresses. Network administrators should also consider implementing rate limiting on IPv4 packet processing to prevent excessive CPU consumption during attack scenarios. Cisco recommends upgrading to software versions that contain the specific patches addressing CSCvd80714, which typically involves applying the appropriate IOS XE software release that corrects the IPv4 packet processing logic. Additionally, monitoring systems should be configured to detect unusual CPU utilization patterns and traceback messages that may indicate exploitation attempts. Network segmentation and firewall rules can further limit the attack surface by restricting which IPv4 addresses can receive traffic from external sources. The vulnerability aligns with CWE-129 and CWE-399 categories related to input validation and resource management, and represents a typical ATT&CK technique for network denial of service attacks through resource exhaustion.