CVE-2023-44190 in Junos OS
Summary
by MITRE • 10/25/2023
An Origin Validation vulnerability in MAC address validation of Juniper Networks Junos OS Evolved on PTX10001, PTX10004, PTX10008, and PTX10016 devices allows a network-adjacent attacker to bypass MAC address checking, allowing MAC addresses not intended to reach the adjacent LAN to be forwarded to the downstream network. Due to this issue, the router will start forwarding traffic if a valid route is present in forwarding-table, causing a loop and congestion in the downstream layer-2 domain connected to the device.
This issue affects Juniper Networks Junos OS Evolved on PTX10001, PTX10004, PTX10008, and PTX10016:
* All versions prior to 21.4R3-S5-EVO; * 22.1 versions prior to 22.1R3-S4-EVO; * 22.2 versions 22.2R1-EVO and later; * 22.3 versions prior to 22.3R2-S2-EVO, 22.3R3-S1-EVO; * 22.4 versions prior to 22.4R2-S1-EVO, 22.4R3-EVO; * 23.2 versions prior to 23.2R1-S1-EVO, 23.2R2-EVO.
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Analysis
by VulDB Data Team • 04/29/2026
This vulnerability represents a critical origin validation flaw in the MAC address handling mechanisms of Juniper Networks Junos OS Evolved platforms, specifically impacting the PTX10001, PTX10004, PTX10008, and PTX10016 device families. The issue stems from insufficient validation of MAC addresses within the forwarding table processing logic, creating a pathway for malicious actors to bypass legitimate MAC address restrictions. This vulnerability operates at the Layer 2 network level and fundamentally undermines the security controls designed to prevent unauthorized network access and traffic routing. The flaw enables an attacker positioned on the same network segment to inject MAC addresses that would normally be rejected by the system's access control mechanisms. This represents a significant deviation from expected network behavior where devices should enforce strict MAC address validation before forwarding traffic to downstream network segments.
The technical implementation of this vulnerability occurs within the routing and forwarding table processing components of the Junos OS Evolved software stack. When a valid route exists in the forwarding table, the system incorrectly processes MAC addresses that should be rejected due to origin validation failures. This creates a condition where the router begins forwarding traffic destined for unauthorized MAC addresses, effectively allowing traffic to be transmitted through the network infrastructure without proper authentication or authorization checks. The underlying issue manifests as a failure in the MAC address validation routine that should normally prevent the acceptance of addresses not originating from legitimate sources within the local network segment. This flaw specifically affects the packet forwarding logic and can be exploited by an attacker who has network adjacency to the affected devices, making it particularly dangerous in environments where network segmentation is critical.
The operational impact of this vulnerability extends beyond simple unauthorized access to create serious network stability and security concerns. When exploited, the vulnerability can cause network loops and congestion in downstream Layer 2 domains, as traffic flows that should be restricted begin to propagate throughout the network infrastructure. This creates a denial of service condition where legitimate network traffic experiences performance degradation or complete disruption. The vulnerability essentially allows an attacker to bypass network access controls and potentially gain visibility into network segments that should be protected from direct access. Network administrators may experience unexpected traffic patterns and performance issues that could mask the actual security breach. The impact is particularly severe in high-availability network environments where network loops can cause cascading failures across multiple network segments.
The vulnerability aligns with CWE-284, which describes improper access control in software implementations, and relates to ATT&CK technique T1046, which involves network service scanning and exploitation of network infrastructure. Organizations should implement immediate mitigation strategies including applying the relevant security patches provided by Juniper Networks, implementing network segmentation controls, and monitoring for anomalous traffic patterns that could indicate exploitation attempts. The affected versions span multiple software releases, indicating this is not a simple patchable issue but rather a systemic problem in the software architecture. Network administrators should prioritize updating their affected devices to versions that have been patched, particularly focusing on the specific version ranges mentioned in the vulnerability advisory. Additionally, implementing enhanced monitoring of Layer 2 network traffic and MAC address changes can help detect exploitation attempts before they cause significant network disruption. The vulnerability demonstrates the importance of proper origin validation in network infrastructure devices and highlights the need for comprehensive security testing of routing and forwarding logic in network operating systems.