CVE-2025-7693: CIP Forward Close Packet DoS Vulnerability

CVE-2025-7693 Overview

CVE-2025-7693 is an input validation vulnerability affecting Rockwell Automation controllers. The flaw stems from improper handling of malformed Common Industrial Protocol (CIP) Forward Close packets. An unauthenticated attacker on the network can send crafted CIP packets to force the controller into a fault state. The controller enters a solid red Fault LED state and becomes unresponsive. After a power cycle, the controller enters a recoverable fault state with flashing red MS and Fault LEDs, reporting fault code 0xF015. Recovery requires manually clearing the fault. The vulnerability is categorized under [CWE-20] Improper Input Validation.

Critical Impact
A remote, unauthenticated attacker can render the controller unresponsive by sending malformed CIP Forward Close packets, causing operational disruption in industrial environments.

Affected Products

Rockwell Automation industrial controllers (see vendor advisory SD1736 for specific models and firmware versions)
Devices implementing the CIP Forward Close service
Industrial Control System (ICS) deployments using affected Rockwell controllers

Discovery Timeline

2025-08-18 - CVE-2025-7693 published to the National Vulnerability Database
2026-04-15 - Last updated in NVD database

Technical Details for CVE-2025-7693

Vulnerability Analysis

The vulnerability resides in the controller's CIP protocol stack, specifically in the routine that processes Forward Close service requests. CIP Forward Close is used to terminate established connections between CIP endpoints. The affected controllers fail to validate malformed Forward Close packet structures before processing them. When such packets reach the controller, the firmware enters an unrecoverable fault state indicated by a solid red Fault LED. The device stops processing further requests, halting any control logic execution dependent on the controller.

After a power cycle, the controller transitions into a recoverable fault state. The MS LED and Fault LED both flash red, and the controller reports fault code 0xF015. Operators must manually clear the fault to restore normal operation. This behavior indicates that the malformed packet triggers a persistent error state stored across reboots, requiring administrative action.

Root Cause

The root cause is improper input validation [CWE-20] within the CIP Forward Close handler. The controller firmware does not adequately verify packet structure, field sizes, or parameter consistency before parsing the message. Malformed inputs propagate into internal state logic, causing the firmware to halt execution and assert a fault condition.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker with network reachability to the controller's CIP service can send crafted Forward Close packets. CIP commonly runs over EtherNet/IP on TCP port 44818 and UDP port 2222. Any host able to route to the controller's industrial network segment can deliver the payload.

No verified proof-of-concept code is publicly available. The vulnerability was identified through fuzzing of the CIP protocol implementation, as referenced in the Rockwell Security Advisory SD1736.

Detection Methods for CVE-2025-7693

Indicators of Compromise

Controller fault code 0xF015 reported after a power cycle
Solid red Fault LED on the controller, with the device becoming unresponsive to engineering workstation requests
Flashing red MS LED and Fault LED following recovery attempts
Unexpected loss of process visibility or control logic execution on affected programmable logic controllers

Detection Strategies

Monitor industrial network traffic for malformed CIP Forward Close service requests directed at controllers
Deploy ICS-aware network intrusion detection sensors that decode EtherNet/IP and CIP protocols
Correlate controller fault events with network packet captures to identify attacker-sourced traffic
Use asset inventory tools to track firmware versions of Rockwell controllers against the vendor advisory SD1736

Monitoring Recommendations

Forward controller diagnostic messages and fault codes to a centralized log management or SIEM platform
Establish baseline CIP traffic patterns and alert on anomalous Forward Close request volumes or malformed structures
Monitor TCP port 44818 and UDP port 2222 connections from unauthorized sources on the operational technology network
Track engineering workstation activity that precedes controller fault events

How to Mitigate CVE-2025-7693

Immediate Actions Required

Review the Rockwell Security Advisory SD1736 and identify affected controller models and firmware versions in your environment
Apply the vendor-supplied firmware updates referenced in the advisory as soon as operational change windows permit
Restrict network access to controllers using firewalls and network segmentation, allowing CIP traffic only from authorized engineering workstations
Clear any active fault state on impacted controllers and verify operational integrity before returning them to production

Patch Information

Rockwell Automation has published remediation guidance in advisory SD1736. Refer to the Rockwell Security Advisory SD1736 for the list of fixed firmware versions and upgrade procedures. Apply the patched firmware following the vendor's recommended deployment process for industrial controllers.

Workarounds

Place affected controllers behind a properly configured industrial firewall that filters CIP traffic by source and destination
Implement network segmentation following ISA/IEC 62443 zones-and-conduits guidance to isolate controllers from general IT networks
Disable or block CIP services on controllers where the Forward Close capability is not required for operations
Restrict EtherNet/IP traffic (TCP 44818, UDP 2222) at perimeter and internal firewalls to known authorized hosts only

bash

# Example firewall rule to restrict CIP traffic to authorized engineering workstation
iptables -A FORWARD -p tcp --dport 44818 -s <authorized_workstation_ip> -d <controller_ip> -j ACCEPT
iptables -A FORWARD -p tcp --dport 44818 -d <controller_ip> -j DROP
iptables -A FORWARD -p udp --dport 2222 -d <controller_ip> -j DROP