CVE-2023-3595: Rockwell Automation ControlLogix RCE Flaw

CVE-2023-3595 Overview

CVE-2023-3595 is a critical out-of-bounds write vulnerability affecting Rockwell Automation 1756 EN2* and 1756 EN3* ControlLogix communication products. This vulnerability enables a malicious user to perform remote code execution with persistence on the target system through maliciously crafted CIP (Common Industrial Protocol) messages. The exploitation includes the ability to modify, deny, and exfiltrate data passing through the device, posing significant risks to industrial control systems and operational technology environments.

Critical Impact

Remote code execution with persistence capability on industrial control systems, allowing attackers to modify, deny, and exfiltrate operational data passing through affected ControlLogix communication modules.

Affected Products

• Rockwell Automation 1756-EN2F Series A, B, and C Firmware
• Rockwell Automation 1756-EN2T Series A, B, C, and D Firmware
• Rockwell Automation 1756-EN2TR Series A, B, and C Firmware
• Rockwell Automation 1756-EN3TR Series A and B Firmware

Discovery Timeline

• July 12, 2023 - CVE-2023-3595 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2023-3595

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-Bounds Write), which occurs when the software writes data past the end, or before the beginning, of the intended buffer. In the context of ControlLogix communication modules, the vulnerability exists in how the devices process CIP messages. When a specially crafted CIP message is received, the device fails to properly validate the boundaries of the write operation, allowing an attacker to write arbitrary data to memory locations outside the intended buffer.

The impact is particularly severe for industrial control systems because successful exploitation grants the attacker the ability to execute code with persistence, meaning the malicious code survives device reboots. This persistence mechanism allows for long-term compromise of critical infrastructure systems. Additionally, the attacker gains the capability to intercept, modify, or block legitimate data traffic passing through the communication module, potentially disrupting industrial processes or injecting false data into control systems.

Root Cause

The root cause of CVE-2023-3595 lies in insufficient bounds checking when processing CIP protocol messages within the ControlLogix communication module firmware. The affected devices do not adequately validate the length and content of incoming CIP messages before writing data to internal memory buffers. This lack of input validation allows attackers to send malformed packets that trigger out-of-bounds memory writes, ultimately leading to code execution in a privileged context on the device.

Attack Vector

The attack vector for this vulnerability is network-based, requiring no authentication, privileges, or user interaction. An attacker with network access to the affected ControlLogix communication module can craft malicious CIP messages targeting the vulnerable parsing functionality. The Common Industrial Protocol (CIP) is widely used in industrial automation environments for communication between controllers, I/O devices, and human-machine interfaces.

The attack flow proceeds as follows: The attacker sends specially crafted CIP messages over the network to the target communication module. These messages contain payload data designed to trigger the out-of-bounds write condition. Once the vulnerable code path is reached, the attacker's payload is written to an unintended memory location, enabling arbitrary code execution. The persistence mechanism allows the malicious code to survive device restarts, establishing a long-term foothold in the industrial environment.

Detection Methods for CVE-2023-3595

Indicators of Compromise

• Unexpected CIP traffic patterns or malformed CIP messages targeting ControlLogix communication modules on ports 2222/TCP and 44818/TCP
• Anomalous behavior in 1756-EN2* or 1756-EN3* modules such as unexpected reboots, configuration changes, or communication disruptions
• Unexplained modifications to device firmware or configuration that persist across reboots
• Data exfiltration attempts or unusual outbound network connections from industrial network segments

Detection Strategies

• Deploy network intrusion detection systems (NIDS) with rules specifically designed to identify malformed or suspicious CIP protocol traffic
• Implement deep packet inspection for EtherNet/IP and CIP communications to detect exploitation attempts
• Enable comprehensive logging on network devices and monitor for connections to ControlLogix modules from unauthorized sources
• Utilize industrial control system (ICS) security monitoring solutions to baseline normal communication patterns and alert on deviations

Monitoring Recommendations

• Establish continuous network monitoring of all traffic to and from ControlLogix communication modules
• Implement firmware integrity verification checks to detect unauthorized modifications to device firmware
• Monitor for unexpected data flow patterns that may indicate data modification or exfiltration through compromised devices
• Review access logs and authentication attempts for the industrial network segment containing affected devices

How to Mitigate CVE-2023-3595

Immediate Actions Required

• Apply firmware updates provided by Rockwell Automation as soon as possible for all affected 1756-EN2* and 1756-EN3* series communication modules
• Implement network segmentation to isolate ControlLogix systems from untrusted networks and limit exposure to potential attackers
• Restrict network access to affected devices using firewalls and access control lists, allowing only authorized systems to communicate via CIP
• Disable any unnecessary network services and ports on affected devices to reduce the attack surface

Patch Information

Rockwell Automation has released security patches to address CVE-2023-3595. Organizations should consult the Rockwell Automation Security Advisory for specific firmware versions that address this vulnerability and detailed patching instructions. Given the critical nature of this vulnerability and its potential impact on industrial operations, prioritize patching affected communication modules during the next available maintenance window.

Workarounds

• Implement strict network segmentation to isolate affected ControlLogix communication modules from untrusted networks and the internet
• Deploy application-layer firewalls capable of inspecting and filtering CIP protocol traffic to block potentially malicious messages
• Use a demilitarized zone (DMZ) architecture for any systems that require connectivity between industrial and enterprise networks
• Enable CIP security features where available and configure allowlists for authorized CIP connections to the affected modules

# Network segmentation example using iptables to restrict CIP access
# Allow CIP traffic only from authorized engineering workstations
iptables -A INPUT -p tcp --dport 44818 -s 192.168.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 2222 -s 192.168.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 44818 -j DROP
iptables -A INPUT -p tcp --dport 2222 -j DROP