CVE-2022-22191 in Junos OS
Summary
by MITRE • 04/14/2022
A Denial of Service (DoS) vulnerability in the processing of a flood of specific ARP traffic in Juniper Networks Junos OS on the EX4300 switch, sent from the local broadcast domain, may allow an unauthenticated network-adjacent attacker to trigger a PFEMAN watchdog timeout, causing the Packet Forwarding Engine (PFE) to crash and restart. After the restart, transit traffic will be temporarily interrupted until the PFE is reprogrammed. In a virtual chassis (VC), the impacted Flexible PIC Concentrator (FPC) may split from the VC temporarily, and join back into the VC once the PFE restarts. Continued receipt and processing of these packets will create a sustained Denial of Service (DoS) condition. This issue affects Juniper Networks Junos OS on the EX4300: All versions prior to 15.1R7-S12; 18.4 versions prior to 18.4R2-S10, 18.4R3-S11; 19.1 versions prior to 19.1R3-S8; 19.2 versions prior to 19.2R1-S9, 19.2R3-S4; 19.3 versions prior to 19.3R3-S5; 19.4 versions prior to 19.4R2-S6, 19.4R3-S7; 20.1 versions prior to 20.1R3-S3; 20.2 versions prior to 20.2R3-S3; 20.3 versions prior to 20.3R3-S2; 20.4 versions prior to 20.4R3-S1; 21.1 versions prior to 21.1R3; 21.2 versions prior to 21.2R2-S1, 21.2R3; 21.3 versions prior to 21.3R1-S2, 21.3R2.
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Analysis
by VulDB Data Team • 04/20/2022
This vulnerability represents a significant denial of service threat targeting the Packet Forwarding Engine (PFE) of Juniper Networks EX4300 switches running affected versions of Junos OS. The flaw manifests when the device receives a flood of specifically crafted ARP traffic originating from the local broadcast domain, enabling unauthenticated attackers positioned within the network adjacent to the affected switch to exploit this weakness. The attack leverages the PFE's handling of ARP packets, triggering a PFEMAN watchdog timeout that results in the complete crash and subsequent restart of the Packet Forwarding Engine. This behavior aligns with CWE-400 vulnerability classification related to unspecified resource exhaustion, where the system's resources become consumed to the point of system instability.
The technical implementation of this vulnerability occurs within the ARP processing logic of the PFE component, where the system fails to properly handle the volume and specific characteristics of malicious ARP traffic. When the watchdog timer expires due to excessive packet processing demands, it initiates an automatic restart sequence that disrupts normal network operations. The restart process creates temporary transit traffic interruptions as the PFE reprograms itself, effectively creating a service disruption that can persist until the restart completes. This mechanism operates at the network layer where the PFE processes forwarding decisions, making it particularly impactful as it affects the core forwarding functionality of the switch.
The operational impact extends beyond simple service interruption, as this vulnerability can be sustained through continuous packet flooding, creating a persistent denial of service condition that can severely impact network availability. In virtual chassis configurations, the affected Flexible PIC Concentrator (FPC) may temporarily detach from the virtual chassis and rejoin once the PFE restarts, causing additional disruption to the overall network topology and potentially affecting multiple network segments simultaneously. The vulnerability affects a broad range of Junos OS versions across multiple release branches, indicating this is not a recent issue but rather a long-standing flaw in the ARP handling implementation that has persisted across several major releases.
The attack vector requires only network adjacency, making it particularly concerning as it can be executed by attackers who are physically present within the same broadcast domain or have access to network segments that can reach the affected switch. This aligns with ATT&CK framework technique T1498.001 related to Network Denial of Service, where adversaries leverage system vulnerabilities to exhaust resources and cause service disruption. Organizations running affected Juniper EX4300 switches are particularly vulnerable as these devices are commonly deployed in enterprise and service provider environments where network availability is critical. The vulnerability demonstrates a lack of proper input validation and resource management in the ARP processing subsystem, allowing malicious packet flooding to trigger system instability.
Mitigation strategies should focus on immediate patching of affected systems with the vendor-provided security updates, which address the underlying ARP processing logic to prevent the watchdog timeout condition. Network administrators should also implement rate limiting and access control measures to restrict ARP traffic from untrusted sources, particularly within the local broadcast domain. Monitoring systems should be configured to detect unusual ARP traffic patterns that may indicate exploitation attempts, while network segmentation strategies can help limit the impact scope if an attack is successfully launched. The vulnerability highlights the importance of proper resource management and input validation in network infrastructure devices, as outlined in industry best practices for secure network design and the principles of least privilege in network security architecture.