CVE-2024-20267 in NX-OS
Summary
by MITRE • 02/29/2024
A vulnerability with the handling of MPLS traffic for Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause the netstack process to unexpectedly restart, which could cause the device to stop processing network traffic or to reload.
This vulnerability is due to lack of proper error checking when processing an ingress MPLS frame. An attacker could exploit this vulnerability by sending a crafted IPv6 packet that is encapsulated within an MPLS frame to an MPLS-enabled interface of the targeted device. A successful exploit could allow the attacker to cause a denial of service (DoS) condition.
Note: The IPv6 packet can be generated multiple hops away from the targeted device and then encapsulated within MPLS. The DoS condition may occur when the NX-OS device processes the packet.
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Analysis
by VulDB Data Team • 04/03/2024
This vulnerability resides in Cisco NX-OS Software's handling of multiprotocol label switching traffic and represents a significant denial of service risk that could compromise network infrastructure availability. The flaw manifests when the software processes ingress MPLS frames without adequate error validation mechanisms, creating a condition where malformed or crafted packets can trigger unexpected system behavior. The vulnerability specifically affects devices with MPLS capabilities enabled, making it particularly concerning for service providers and enterprise networks that rely heavily on MPLS for traffic engineering and quality of service implementations. According to the Common Weakness Enumeration catalog, this vulnerability maps to CWE-248, which describes an "Uncaught Exception" scenario where an application fails to properly handle exceptional conditions during processing. The attack vector requires an unauthenticated remote adversary who can inject specially crafted IPv6 packets that are then encapsulated within MPLS frames, allowing exploitation from multiple network hops away from the target device.
The technical implementation of this vulnerability stems from insufficient input validation within the netstack process responsible for MPLS packet processing. When the NX-OS software receives an MPLS frame containing a malformed IPv6 packet, the lack of proper error checking causes the system to crash or restart the netstack component. This behavior constitutes a classic denial of service condition that can effectively render network services unavailable to legitimate users. The vulnerability's remote nature means that attackers do not require physical access or network credentials to exploit the flaw, making it particularly dangerous in publicly accessible network segments. The attack can be executed from any location where the attacker can influence traffic reaching the targeted MPLS-enabled interface, potentially allowing for coordinated attacks against critical network infrastructure components.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise network reliability and availability for extended periods. When the netstack process restarts, the device may experience complete cessation of MPLS traffic processing, affecting all services dependent on MPLS-based routing and forwarding. In some cases, the device may automatically reload to recover from the crash, causing additional network disruption as routing tables are rebuilt and connections are re-established. For enterprise networks relying on MPLS for core routing functions, this vulnerability could result in significant business impact, particularly in scenarios where network availability is critical for business operations. The vulnerability's exploitation does not require advanced privileges or specialized tools, making it accessible to a broad range of threat actors and increasing the potential for widespread impact across multiple network segments.
Mitigation strategies should focus on immediate network segmentation and access control measures to prevent unauthorized access to MPLS-enabled interfaces. Network administrators should implement ingress filtering and MPLS traffic validation mechanisms to detect and prevent malformed packets from reaching vulnerable devices. The recommended approach includes applying Cisco's official security advisories and patches as soon as they become available, while also implementing monitoring solutions to detect unusual restart patterns or netstack behavior that might indicate exploitation attempts. According to the MITRE ATT&CK framework, this vulnerability aligns with techniques involving privilege escalation and denial of service, specifically mapping to T1499.004 for network denial of service and T1071.004 for application layer protocol usage. Organizations should also consider implementing redundant network paths and failover mechanisms to minimize the impact of potential exploitation, while maintaining detailed logging and alerting capabilities to detect and respond to exploitation attempts in real-time.