CVE-2014-3321 in IOS
Summary
by MITRE
Cisco IOS XR 4.3.4 and earlier on ASR 9000 devices, when bridge-group virtual interface (BVI) routing is enabled, allows remote attackers to cause a denial of service (chip and card hangs) via a series of crafted MPLS packets, aka Bug ID CSCuo91149.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 02/09/2022
This vulnerability affects Cisco IOS XR software version 4.3.4 and earlier running on ASR 9000 series routers where bridge-group virtual interface routing is enabled. The flaw manifests as a remote denial of service condition that can cause complete system failure through chip and card hangs. The vulnerability specifically targets the handling of MPLS packets within the BVI routing context, creating a scenario where maliciously crafted packet sequences can trigger system instability. The attack vector is remote, meaning an attacker does not need physical access to the device to exploit this weakness, making it particularly concerning for network infrastructure devices that are often exposed to external networks.
The technical root cause lies in the improper handling of MPLS packet processing when BVI routing is active. When the system receives a series of specially crafted MPLS packets, the packet processing logic fails to properly validate or handle the packet structures, leading to resource exhaustion or state corruption within the forwarding plane. This vulnerability is particularly dangerous because it operates at the hardware level within the routing chip, causing the entire card or chip to hang rather than simply disrupting routing operations. The issue is classified as a buffer overflow or memory corruption vulnerability that can be triggered through network traffic processing, making it a critical concern for network availability.
The operational impact of this vulnerability extends beyond simple service disruption to potentially causing complete network outages. When the chip or card hangs, the affected routing engine becomes unresponsive, leading to loss of routing functionality for all traffic passing through that hardware component. This can result in cascading failures throughout the network infrastructure, as traffic may be rerouted through backup paths or fail completely if no redundancy exists. The vulnerability affects enterprise and service provider networks where ASR 9000 routers serve as core infrastructure components, potentially impacting thousands of connected devices and services. The remote nature of the attack means that malicious actors can exploit this vulnerability from anywhere on the internet without requiring network access to the device itself.
Mitigation strategies for this vulnerability include applying the appropriate Cisco security patches and updates that address the MPLS packet handling logic within the BVI routing context. Network administrators should also implement traffic filtering measures to prevent suspicious MPLS packets from reaching affected devices, particularly at network boundaries. The implementation of monitoring and alerting systems can help detect anomalous packet patterns that may indicate exploitation attempts. Additionally, network segmentation and the use of firewalls to restrict MPLS traffic can provide additional layers of protection. Organizations should also review their network architecture to ensure proper redundancy exists, as this vulnerability can cause complete card failures that may not be immediately recoverable through standard software restarts. This vulnerability aligns with CWE-121 and CWE-122 categories related to buffer overflow conditions, and represents a significant concern for the ATT&CK framework under the T1499 category of Network Denial of Service, demonstrating how infrastructure-level vulnerabilities can be leveraged to create widespread service disruption.