CVE-2026-9140: 1719-AENTR DoS Vulnerability

CVE-2026-9140 Overview

CVE-2026-9140 is a denial-of-service vulnerability affecting the Rockwell Automation 1719-AENTR EtherNet/IP adapter. The device improperly handles a User Datagram Protocol (UDP) unicast network storm, which causes it to become overloaded and lose communication. Recovery requires a manual power cycle, making this issue particularly disruptive in industrial control environments where uptime is critical. The vulnerability is categorized under CWE-770: Allocation of Resources Without Limits or Throttling and is exploitable remotely over the network without authentication or user interaction.

Critical Impact
An unauthenticated remote attacker can send a sustained UDP unicast flood to the 1719-AENTR adapter, forcing the device into an unresponsive state that requires a physical power cycle to restore operations.

Affected Products

Rockwell Automation 1719-AENTR EtherNet/IP Adapter
Industrial control systems relying on the 1719-AENTR for I/O communication
Deployments using the affected adapter within EtherNet/IP-based operational technology (OT) networks

Discovery Timeline

2026-07-14 - CVE-2026-9140 published to the National Vulnerability Database (NVD)
2026-07-14 - Last updated in NVD database
Advisory Reference - Rockwell Automation Security Advisory SD1778

Technical Details for CVE-2026-9140

Vulnerability Analysis

The 1719-AENTR adapter fails to throttle or gracefully handle large volumes of inbound UDP unicast traffic. When a network storm targets the device, its internal processing and networking resources become saturated. This resource exhaustion condition prevents the adapter from servicing legitimate EtherNet/IP requests, breaking communication with connected controllers and I/O modules. Because the device does not self-recover after the traffic subsides, operators must manually power-cycle the unit to return it to a functional state. In industrial environments, this loss of communication can halt automated processes, interrupt safety monitoring, and require manual intervention on the plant floor.

Root Cause

The root cause is improper resource management on the adapter's network stack, aligning with CWE-770. The device does not enforce sufficient rate limiting, connection throttling, or packet-processing safeguards to absorb high-volume UDP unicast traffic. Once the internal buffers or processing queues reach capacity, the adapter's networking subsystem enters a hung state and cannot recover autonomously.

Attack Vector

The attack vector is network-based and requires no authentication, no privileges, and no user interaction. An attacker with the ability to send UDP packets to the adapter's IP address, either from within the OT network or through an exposed management path, can trigger the condition. The exploitation technique is a UDP unicast flood directed at the adapter, sustained long enough to overwhelm the device. Because the vulnerability affects availability only, it does not permit code execution or data disclosure, but it can cause meaningful operational disruption in production environments. See the Rockwell Automation Security Advisory SD1778 for vendor-specific technical details.

Detection Methods for CVE-2026-9140

Indicators of Compromise

Sudden and sustained bursts of UDP unicast traffic directed at 1719-AENTR adapter IP addresses.
Loss of EtherNet/IP communication between controllers and I/O modules serviced by the adapter.
Adapter unresponsiveness on management interfaces until a manual power cycle is performed.
Unusual east-west UDP traffic patterns originating from non-engineering workstations or unmanaged devices on the OT network.

Detection Strategies

Deploy network traffic monitoring on OT segments to flag UDP unicast volume anomalies against the adapter's IP.
Correlate controller communication loss events with concurrent spikes in UDP traffic to affected devices.
Use industrial intrusion detection systems (IDS) with EtherNet/IP protocol awareness to identify abnormal traffic behavior.

Monitoring Recommendations

Baseline normal EtherNet/IP and UDP traffic to and from 1719-AENTR adapters, then alert on deviations.
Monitor adapter health and connection status via the parent programmable logic controller (PLC) diagnostics.
Log and alert on repeated power-cycle events for affected adapters, as they may indicate exploitation attempts.

How to Mitigate CVE-2026-9140

Immediate Actions Required

Consult Rockwell Automation Security Advisory SD1778 and apply vendor-recommended firmware updates when available.
Restrict network access to 1719-AENTR adapters through segmentation, allowing only trusted controllers and engineering workstations to communicate with them.
Block or rate-limit UDP unicast traffic to the adapter from untrusted network segments at the industrial firewall.
Verify that OT networks are not directly reachable from the internet or enterprise IT networks.

Patch Information

Refer to the Rockwell Automation Security Advisory SD1778 for authoritative patch, firmware version, and configuration guidance from the vendor. Apply firmware updates during a planned maintenance window and validate device behavior after upgrade.

Workarounds

Implement strict access control lists (ACLs) on OT switches and industrial firewalls to permit EtherNet/IP traffic only from authorized controllers.
Enable UDP rate limiting or storm control features on managed switches that connect to the adapter.
Isolate the 1719-AENTR adapter on a dedicated VLAN with minimal exposure to general-purpose network traffic.
Establish operational playbooks for rapid physical recovery, including remote-controlled power distribution units where safe and appropriate.

bash

# Example: Cisco-style storm control on a switch port connected to a 1719-AENTR adapter
interface GigabitEthernet0/5
 description Link to 1719-AENTR adapter
 storm-control unicast level pps 1000
 storm-control action shutdown
 switchport mode access
 switchport access vlan 20