CVE-2018-0239 in ASR 5700
Summary
by MITRE
A vulnerability in the egress packet processing functionality of the Cisco StarOS operating system for Cisco Aggregation Services Router (ASR) 5700 Series devices and Virtualized Packet Core (VPC) System Software could allow an unauthenticated, remote attacker to cause an interface on the device to cease forwarding packets. The device may need to be manually reloaded to clear this Interface Forwarding Denial of Service condition. The vulnerability is due to the failure to properly check that the length of a packet to transmit does not exceed the maximum supported length of the network interface card (NIC). An attacker could exploit this vulnerability by sending a crafted IP packet or a series of crafted IP fragments through an interface on the targeted device. A successful exploit could allow the attacker to cause the network interface to cease forwarding packets. This vulnerability could be triggered by either IPv4 or IPv6 network traffic. This vulnerability affects the following Cisco products when they are running the StarOS operating system and a virtual interface card is installed on the device: Aggregation Services Router (ASR) 5700 Series, Virtualized Packet Core-Distributed Instance (VPC-DI) System Software, Virtualized Packet Core-Single Instance (VPC-SI) System Software. Cisco Bug IDs: CSCvf32385.
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Analysis
by VulDB Data Team • 03/03/2023
This vulnerability exists within the egress packet processing functionality of Cisco StarOS operating system affecting critical network infrastructure devices. The flaw represents a denial of service condition that can be triggered remotely without authentication, making it particularly dangerous for network availability. The vulnerability specifically impacts Cisco Aggregation Services Router 5700 Series devices and Virtualized Packet Core System Software implementations, where the operating system fails to properly validate packet length parameters against hardware interface limitations. This weakness creates a scenario where an attacker can manipulate network traffic to cause complete forwarding cessation on targeted interfaces, requiring manual device reloads to restore normal operations. The vulnerability stems from inadequate input validation mechanisms that should enforce maximum transmission unit boundaries for network interface cards.
The technical exploitation of this vulnerability occurs through the transmission of specially crafted IP packets or fragmented IP packets to targeted interfaces. The flaw manifests when the system does not verify that packet lengths remain within the maximum supported dimensions of the network interface card hardware. This validation failure allows packets that exceed interface capacity to be processed in a manner that causes the interface to stop forwarding traffic entirely. The attack vector is particularly concerning as it operates over both IPv4 and IPv6 protocols, expanding the potential attack surface and making the vulnerability applicable across modern network environments. The vulnerability is classified as a buffer overflow condition in the packet processing pipeline, where the system fails to implement proper bounds checking before packet transmission. This type of vulnerability commonly maps to CWE-129 Input Validation and Output Processing, where insufficient validation of input parameters leads to system instability.
The operational impact of this vulnerability extends beyond simple service disruption to create significant reliability concerns for network infrastructure. When an interface ceases forwarding packets, it creates network outages that can affect multiple services depending on the interface's role within the network topology. The requirement for manual device reloads introduces additional operational overhead and potential for extended downtime during incident response. Network administrators must maintain awareness of this vulnerability's potential impact on service availability, particularly in mission-critical environments where network uptime is essential. The vulnerability's remote nature means that attackers can exploit it from external network positions without requiring physical access or elevated privileges, making it particularly attractive for malicious actors seeking to disrupt network services. This characteristic aligns with ATT&CK technique T1499.004 Network Denial of Service, where adversaries target network infrastructure to cause service disruption.
Mitigation strategies for this vulnerability should focus on implementing immediate network segmentation and access control measures to limit potential attack vectors. Network administrators should deploy ingress filtering and egress filtering policies to restrict packet transmission patterns that could trigger the vulnerability. The most effective long-term solution involves applying the vendor-provided security patches and firmware updates that address the packet length validation deficiencies. Additionally, implementing monitoring systems that can detect unusual packet patterns or interface behavior changes can provide early warning of potential exploitation attempts. Network teams should also consider implementing redundant network paths and failover mechanisms to minimize the impact of interface failures. The vulnerability highlights the importance of proper input validation in network operating system implementations and underscores the need for comprehensive testing of packet processing functions against boundary conditions. Organizations should conduct regular vulnerability assessments and penetration testing to identify similar validation weaknesses in their network infrastructure components.