CVE-2023-1935: Emerson ROC809 Authentication Bypass Flaw

CVE-2023-1935 Overview

CVE-2023-1935 is an authentication bypass vulnerability affecting Emerson ROC800-Series Remote Terminal Unit (RTU) devices used in oil and gas industrial control system (ICS) environments. The flaw allows an unauthenticated attacker with network access to gain unauthorized access to device data, take control of the RTU, or trigger a denial-of-service condition. The vulnerability is tracked under [CWE-287] (Improper Authentication) and was published in the National Vulnerability Database (NVD) on August 2, 2023. CISA published advisory ICSA-23-206-03 covering the affected Emerson product line.

Critical Impact
An unauthenticated remote attacker can bypass authentication on ROC800-Series RTUs to read process data, manipulate device control, or cause loss of availability in operational technology environments.

Affected Products

Emerson ROC809 and ROC809L RTUs (and associated firmware)
Emerson ROC827 and ROC827L RTUs (and associated firmware)
Emerson DL8000 RTU (and associated firmware)

Discovery Timeline

2023-08-02 - CVE-2023-1935 published to the NVD
2024-11-21 - Last updated in the NVD database

Technical Details for CVE-2023-1935

Vulnerability Analysis

The ROC800-Series RTU devices implement an authentication mechanism that can be bypassed over the network. An attacker who can reach the device's management protocol does not need valid credentials, prior access, or user interaction to issue commands the device will accept as authenticated. Because RTUs in this family directly supervise field instrumentation and actuators, the impact extends beyond data exposure to integrity and availability of the physical process under control.

The vulnerability is classified under [CWE-287] Improper Authentication. The EPSS exploit-likelihood data indicates a relatively low predicted exploitation rate at the time of publication, but ICS exposure on operational networks materially raises real-world risk where these devices are reachable from corporate or remote-access segments.

Root Cause

The root cause is improper enforcement of authentication within the proprietary protocol used to manage the ROC800-Series controllers. Authentication state is not adequately validated before privileged operations are honored, allowing requests that should be rejected to proceed as if the session were authorized.

Attack Vector

Exploitation requires network reachability to the affected RTU on its management protocol port. No credentials, no user interaction, and no prior foothold on the device are required. Once authentication is bypassed, an attacker can read configuration and process variables, issue write or control operations that alter device behavior, or send malformed requests that drive the device into a denial-of-service state. Refer to the CISA ICS Advisory ICSA-23-206-03 for protocol-level technical details.

No verified public proof-of-concept code is available for this vulnerability.
Refer to the CISA ICS advisory for technical details.

Detection Methods for CVE-2023-1935

Indicators of Compromise

Unexpected configuration changes, setpoint modifications, or firmware writes on ROC800-Series RTUs that do not correlate with authorized engineering activity.
Connections to ROC800 management ports from hosts outside the engineering workstation allowlist, or from external/IT network segments.
RTU restarts, watchdog resets, or communication losses following inbound sessions from unexpected sources.

Detection Strategies

Deploy ICS-aware network monitoring that parses Emerson ROC protocol traffic and alerts on authentication-related anomalies and unauthorized write operations.
Compare RTU configuration baselines on a scheduled cadence and alert on any drift not tied to a change-management ticket.
Correlate firewall and jump-host logs with RTU session activity to identify sessions that bypass the documented engineering path.

Monitoring Recommendations

Forward firewall, IDS, and historian logs into a centralized analytics platform and retain them for incident investigation across IT and OT boundaries.
Alert on any new source IP initiating sessions to ROC800 management ports, and on any control-write operations occurring outside maintenance windows.
Monitor RTU availability and unexpected reboots as potential indicators of exploitation attempts.

How to Mitigate CVE-2023-1935

Immediate Actions Required

Inventory all ROC809, ROC809L, ROC827, ROC827L, and DL8000 devices and verify firmware versions against Emerson's current advisory.
Remove ROC800-Series RTUs from any direct internet exposure and place them behind firewalls within a segmented OT network.
Restrict management protocol access to a small, explicitly defined list of engineering workstations and jump hosts.
Require VPN with multi-factor authentication for any remote engineering access to the control network.

Patch Information

No vendor patch URL is provided in the NVD entry. Asset owners should contact Emerson directly and follow the remediation guidance in CISA ICS Advisory ICSA-23-206-03 for firmware updates and configuration hardening applicable to their device revisions.

Workarounds

Apply strict network segmentation between IT and OT environments and block ROC800 management protocols at the perimeter.
Use an allowlist on OT firewalls so only authorized engineering hosts can reach RTU management interfaces.
Disable or restrict remote programming features on the RTU where operationally feasible until firmware remediation is applied.
Increase logging verbosity on firewalls and historians adjacent to affected RTUs to support investigation if compromise is suspected.

bash

# Example: restrict access to ROC800 management ports to a defined engineering subnet
# Replace interfaces, ports, and subnets with values from your environment
iptables -A FORWARD -s 10.20.30.0/24 -d 10.50.0.0/16 -p tcp --dport 4000 -j ACCEPT
iptables -A FORWARD -d 10.50.0.0/16 -p tcp --dport 4000 -j DROP