CVE-2016-1478 in IOS
Summary
by MITRE
Cisco IOS 15.5(3)S3, 15.6(1)S2, 15.6(2)S1, and 15.6(2)T1 does not properly dequeue invalid NTP packets, which allows remote attackers to cause a denial of service (interface wedge) by sending many crafted NTP packets, aka Bug ID CSCva35619.
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Analysis
by VulDB Data Team • 10/14/2024
The vulnerability described in CVE-2016-1478 represents a critical denial of service flaw within Cisco IOS operating systems that affects multiple software releases including 15.5(3)S3, 15.6(1)S2, 15.6(2)S1, and 15.6(2)T1. This issue stems from the improper handling of Network Time Protocol packets within the IOS kernel, specifically when processing invalid NTP packet dequing operations. The flaw manifests when the system receives crafted NTP packets that do not conform to standard protocol specifications, creating a scenario where the network interface becomes unresponsive and enters a wedged state. This vulnerability directly impacts network infrastructure devices that rely on NTP for time synchronization, making it particularly dangerous for enterprise and service provider networks where continuous uptime is critical.
The technical root cause of this vulnerability lies in the insufficient validation and handling of malformed NTP packets within the IOS NTP implementation. When the system encounters invalid NTP packets, the packet processing logic fails to properly dequeue these malformed packets from the network queue, leading to a cascading failure that ultimately results in the network interface becoming non-responsive. This behavior creates a condition where legitimate network traffic cannot be processed while the system remains in a state where it cannot properly handle incoming packets. The vulnerability specifically targets the NTP packet processing module within the IOS kernel, where the lack of proper error handling for invalid packet formats causes the system to enter an unstable state that prevents normal network operations. This issue falls under the category of improper handling of malformed input data, which is classified as CWE-248 in the CWE database, representing an exception handling weakness where the system fails to properly handle error conditions.
The operational impact of this vulnerability is severe and can result in complete network disruption for affected devices. When exploited, the vulnerability allows remote attackers to perform a denial of service attack that can render network interfaces unusable, effectively causing network outages that can last until the device is manually rebooted or the system is reset. The attack requires minimal resources from the attacker, as they only need to send a series of crafted NTP packets to trigger the vulnerability, making it particularly dangerous for networks that are exposed to untrusted network segments. Organizations relying on Cisco IOS devices for critical network infrastructure operations face significant risk from this vulnerability, as it can be exploited by attackers without requiring authentication or elevated privileges. The vulnerability affects the availability aspect of network security by compromising the ability of network interfaces to process legitimate traffic, which can have cascading effects throughout the network infrastructure.
Mitigation strategies for this vulnerability require immediate implementation of Cisco IOS patches and updates that address the NTP packet handling flaw. Network administrators should apply the relevant security patches provided by Cisco as part of their security advisory process, which typically include fixes to the NTP processing logic that properly handle malformed packets. Additionally, implementing network segmentation and access control measures can help reduce the attack surface by limiting exposure of affected devices to untrusted network segments. The implementation of NTP filtering mechanisms and rate limiting for NTP traffic can also provide additional protection against exploitation attempts. Organizations should also consider implementing network monitoring solutions that can detect unusual NTP traffic patterns that may indicate exploitation attempts. From an ATT&CK framework perspective, this vulnerability aligns with the T1499 technique related to network denial of service attacks, and the T1071.004 sub-technique for application layer protocol usage, making it a significant concern for network security operations and incident response teams that must be addressed through both preventive and detective controls to maintain network availability and integrity.