CVE-2020-1665 in Junos
Summary
by MITRE • 10/17/2020
On Juniper Networks MX Series and EX9200 Series, in a certain condition the IPv6 Distributed Denial of Service (DDoS) protection might not take affect when it reaches the threshold condition. The DDoS protection allows the device to continue to function while it is under DDoS attack, protecting both the Routing Engine (RE) and the Flexible PIC Concentrator (FPC) during the DDoS attack. When this issue occurs, the RE and/or the FPC can become overwhelmed, which could disrupt network protocol operations and/or interrupt traffic. This issue does not affect IPv4 DDoS protection. This issue affects MX Series and EX9200 Series with Trio-based PFEs (Packet Forwarding Engines). Please refer to https://kb.juniper.net/KB25385 for the list of Trio-based PFEs. This issue affects Juniper Networks Junos OS on MX series and EX9200 Series: 17.2 versions prior to 17.2R3-S4; 17.2X75 versions prior to 17.2X75-D102, 17.2X75-D110; 17.3 versions prior to 17.3R3-S8; 17.4 versions prior to 17.4R2-S11, 17.4R3-S2; 18.2 versions prior to 18.2R2-S7, 18.2R3, 18.2R3-S3; 18.2X75 versions prior to 18.2X75-D30; 18.3 versions prior to 18.3R2-S4, 18.3R3-S2.
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Analysis
by VulDB Data Team • 11/20/2020
This vulnerability represents a critical failure in the IPv6 distributed denial of service protection mechanism implemented on Juniper Networks MX Series and EX9200 Series routers. The issue manifests when specific threshold conditions are met, causing the DDoS protection system to fail in its intended function of safeguarding network operations during attack scenarios. The vulnerability specifically impacts devices utilizing Trio-based Packet Forwarding Engines, which are responsible for handling packet forwarding operations and maintaining network protocol integrity during high-traffic conditions. The failure occurs exclusively with IPv6 traffic while IPv4 DDoS protection remains unaffected, creating an asymmetric security gap in the network infrastructure. This selective failure pattern suggests a code path or configuration handling difference between IPv4 and IPv6 implementations within the Junos OS operating system.
The technical flaw stems from an incomplete implementation or logic error in the DDoS protection module that governs how IPv6 traffic is monitored and processed during attack conditions. When the threshold conditions are met for IPv6 traffic, the system fails to activate its protective mechanisms that would normally prevent the Routing Engine and Flexible PIC Concentrator from becoming overwhelmed. This failure results in the device continuing to process attack traffic without the necessary rate limiting or traffic filtering that would normally protect the system resources. The vulnerability affects multiple Junos OS versions across different release branches, including 17.2, 17.3, 17.4, 18.2, and 18.3, indicating a widespread issue that spans several major release cycles. The affected versions show specific patch levels that must be reached to remediate the vulnerability, with each release branch having its own set of targeted fixes.
The operational impact of this vulnerability is severe and potentially disruptive to network services. When the DDoS protection fails to activate, the Routing Engine and Flexible PIC Concentrator can become overwhelmed with malicious traffic, leading to performance degradation, protocol disruptions, and potential complete service interruption. The system's inability to protect itself during attack conditions creates a window where network operations become unstable, potentially affecting routing protocols, traffic forwarding, and overall network availability. This vulnerability specifically targets the system's ability to maintain operational integrity during high-traffic attack scenarios, which could result in cascading failures that impact larger network segments. The issue is particularly concerning because it affects core network infrastructure components that are essential for maintaining connectivity and routing operations.
Security implications extend beyond simple service disruption to include potential system compromise and denial of service for legitimate network traffic. The vulnerability creates an attack surface where malicious actors can exploit the incomplete DDoS protection to overwhelm network resources without triggering the expected protective mechanisms. This situation aligns with attack patterns described in the MITRE ATT&CK framework under network denial of service techniques, where attackers can leverage system weaknesses to disrupt service availability. Organizations affected by this vulnerability may experience extended periods of degraded service or complete network outages during attack conditions, particularly when IPv6 traffic is involved. The vulnerability's impact is further amplified by the fact that it affects multiple release versions, meaning organizations across different maintenance cycles may require patch management efforts to achieve full protection. The specific focus on Trio-based PFEs indicates that the vulnerability is tied to particular hardware architectures and their interaction with the Junos OS DDoS protection implementation. Remediation efforts require careful patch management across affected versions, with organizations needing to verify their specific device models and software versions to ensure complete protection against this vulnerability.