CVE-2023-38584

Executive Summary

CVE-2023-38584 is a stack-based buffer overflow vulnerability residing in the Web CGI component of Weintek's cMT3000 series Human-Machine Interface (HMI) devices. The flaw is located in the command_wb.cgi binary and can be triggered by an unauthenticated, anonymous attacker over the network, potentially allowing full control-flow hijacking and complete bypass of login authentication. With a CVSS score of 9.8 and no authentication requirement, this vulnerability exposes industrial control system (ICS) environments to remote compromise of the HMI device, which often acts as the primary operator interface for automated manufacturing and process control systems. Affected products include multiple cMT3000 series models (cMT-FHD, cMT-HDM, cMT3071, cMT3072, cMT3103, cMT3090, cMT3151), and patches are available via specific OS version updates from the vendor.

Technical Analysis

The vulnerability is classified as a stack-based buffer overflow (CWE-121) in the Web CGI subsystem of Weintek cMT3000 series HMI devices. According to the CNA advisory, the flaw resides specifically in the cgi-bin/command_wb.cgi executable. CGIs (Common Gateway Interface) on embedded web servers in HMI/ICS devices are often used to handle administrative commands, parameter updates, and configuration changes via HTTP requests. These interfaces are frequently exposed on the device's network management port and are designed to be reachable by operators on the local network segment.

A stack-based buffer overflow occurs when a program writes data to a fixed-size buffer located on the call stack without adequate bounds checking. When an attacker sends an HTTP request with an input parameter (such as a query string value, POST body parameter, or HTTP header field) that exceeds the allocated buffer size, the excess data overwrites adjacent stack memory — including the saved instruction pointer (return address) and possibly local variables.

In this specific case, the overflow sits within a command-processing CGI, meaning the input surface is likely an argument to a command or a field that command_wb.cgi parses. Because the overflow is triggered before or during an authentication check within the processing flow, an anonymous attacker can overwrite return addresses or authentication flags stored on the stack, thereby bypassing the login requirement entirely. The CNA title explicitly states this dual impact: "hijack control flow and bypass login authentication."

The attack surface is the embedded web server exposed on the network (typically TCP port 80 for HTTP, possibly 443 for HTTPS). Because these HMIs are deployed at the edge of OT networks, they are often accessible from corporate IT networks or even the internet, depending on network segmentation practices. The command_wb.cgi endpoint is likely reachable without any prior session establishment, as the vulnerability bypasses authentication.

The vendor's security bulletin (TEC23005E) confirms that the issue affects multiple models across the cMT3000 product line, and the fix involves updating the device's operating system (firmware) to specific build versions. The fact that a single patch bulletin covers seven distinct products with separate version numbers indicates that the flaw is likely in a shared codebase (the common Web server or CGI library) compiled across the product line.

Exploitation of a stack-based overflow in a CGI process on an embedded device typically yields code execution with the privileges of the web server daemon — often root or a privileged service account on such embedded systems. This makes the vulnerability especially severe, as it could allow an attacker to gain full control over the HMI, modify industrial processes, exfiltrate engineering data, or use the device as a pivot point deeper into the OT network.

Exploitation Scenarios

Note: No public PoC or exploit code is known for CVE-2023-38584 at the time of this writing. The following attack chain is inferred from the vulnerability class (stack-based buffer overflow in an unauthenticated CGI endpoint) and the NVD description. All specific technical references (e.g., command_wb.cgi) come directly from the provided data.

Step 1 — Reconnaissance / Target Identification: An attacker initially performs network reconnaissance to identify exposed Weintek cMT3000 series HMIs. This can be accomplished via Shodan or Censys queries for devices with Weintek-specific HTTP banners, default web server signatures, or known cMT model identifiers in page titles. On the internal network, the attacker may use Nmap service discovery (nmap -p 80,443 --script http-title <target>) or passive network monitoring to locate HMI devices. Given that this is an unauthenticated vulnerability, the attacker does not need valid credentials or prior network access beyond IP reachability.

Step 2 — Triggering the Vulnerability: The attacker crafts a malicious HTTP request targeting the cgi-bin/command_wb.cgi endpoint on the device's web server. The request contains an oversized value in a parameter not explicitly documented in public materials (exact parameter names are redacted from the available disclosure). The request is sent without authentication — no login session, cookie, or token is required. The oversize payload, when parsed by the CGI, overflows a fixed-size stack buffer.

Step 3 — Payload / Execution Method: At the vulnerability-class level, the attacker's payload consists of shellcode or ROP (Return-Oriented Programming) gadgets placed in the overflow data, designed to overwrite the saved return address on the stack. On successful corruption, the CPU retrieves the attacker-controlled return address and jumps to attacker-supplied code or a sequence of existing code gadgets. On embedded ARM or MIPS architectures common in HMI devices, this often involves mapping the stack into an executable region (NX bypass) or using ROP chains to call system() or similar functions. Because the overflow also bypasses the login check (likely by overwriting a stack-resident authentication flag or by redirecting control flow before the authentication routine completes), the attacker gains code execution without valid credentials.

Step 4 — Post-Exploitation: Once code execution is achieved, the attacker assumes the privileges of the web server process — commonly root on embedded devices. The attacker can then: (a) extract or modify HMI configuration files to alter industrial process parameters, (b) upload and execute persistent backdoors (e.g., a custom firmware rootkit or a network backdoor on a high port), (c) capture engineering credentials from the HMI's stored configuration, (d) leverage the device as a pivot node to reach PLCs, RTUs, or other OT equipment on the same automation network, or (e) trigger physical process disruption by altering displayed alarms, masking safety warnings, or directly modifying control logic through the HMI's own protocol bridges. The bypass of login authentication means the attacker does not even need to know the factory-default Web login credentials, eliminating a potential barrier.

In-the-Wild Evidence: As of the time of this report, CISA KEV does not list CVE-2023-38584, and no public exploit code or reported in-the-wild exploitation campaigns have been confirmed. The EPSS score of 0.01051 (61.1st percentile) indicates a relatively low but non-zero probability of exploitation in the short term, warranting monitoring but not immediate public exploits.

Impact Assessment

CVSS Analysis: The CVSS score of 9.8 (Critical) corresponds to: Attack Vector: Network; Attack Complexity: Low; Privileges Required: None; User Interaction: None; Scope: Unchanged; Confidentiality: High; Integrity: High; Availability: High. This reflects a remotely triggerable, unauthenticated, high-impact vulnerability affecting the core security properties of the device.

Business Impact: Weintek cMT3000 series HMIs are deployed in a wide range of industrial automation environments, including manufacturing, process control, packaging, water treatment, and building management systems. The HMI is frequently the operator's sole window into the production process, displaying machine status, alarms, and process trends. Compromise of an HMI can lead to:

• Process manipulation: An attacker can alter alarm thresholds, hide critical safety warnings, or change recipe values transmitted to PLCs, potentially causing defective products, equipment damage, or safety incidents.
• Operational disruption: Ransomware or destructive action on HMI firmware can render the interface inoperable, halting production lines until repair or device replacement.
• Data exfiltration: Stored engineering configurations and production data (e.g., batch records, process recipes) may be extracted.
• Lateral movement: An HMI often has network connectivity to PLCs over protocols such as Modbus, EtherNet/IP, or vendor-specific protocols. A compromised HMI is an ideal pivot for deeper OT network compromise.

Affected Systems: The vulnerability affects seven models in the cMT3000 family — cMT-FHD, cMT-HDM, cMT3071, cMT3072, cMT3103, cMT3090, and cMT3151 — running OS versions prior to the patched builds listed in the vendor advisory. This broad product spread implies a large installed base across the manufacturing sector.

Blast Radius: While the immediate blast radius is the HMI device itself, the indirect impact extends to every downstream PLC, sensor, actuator, and SCADA system communicating with the HMI. In worst-case scenarios, the impact could reach facility safety systems that rely on HMI-based emergency stop or alarm annunciation, elevating potential physical and environmental consequences.

Detection Guidance

The following detection rules are designed to identify exploitation attempts of CVE-2023-38584. They focus on anomalous HTTP requests targeting command_wb.cgi, including oversized parameters, abnormal URI lengths, or unusual request patterns.

Sigma Rule

title: Weintek cMT3000 command_wb.cgi Buffer Overflow Attempt
id: 3f8c5a2e-1b44-4c9e-9e3a-7b2a0a1c5d6e
status: experimental
description: Detects HTTP requests to Weintek cMT3000 HMI command_wb.cgi containing abnormally long parameters, indicative of stack-based buffer overflow exploitation (CVE-2023-38584).
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2023-38584
author: Valtersit Threat Intelligence
date: 2024/01/15
tags:
    - attack.t1190
    - attack.initial-access
    - cve.2023-38584
logsource:
    category: webserver
    product: generic
detection:
    selection:
        cs-uri-path:
            - '*command_wb.cgi*'
        cs-uri-query|length: '> 1024'
    condition: selection
falsepositives:
    - Legitimate but poorly implemented maintenance tools sending long configuration strings
level: high

YARA Rule

rule Weintek_cMT3000_CGI_Overflow_CVE_2023_38584 {
    meta:
        author = "Valtersit Threat Intelligence"
        description = "Detects HTTP request patterns targeting Weintek cMT3000 command_wb.cgi with oversized parameters, indicative of CVE-2023-38584 exploitation"
        date = "2024-01-15"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2023-38584"
        severity = "high"
        cve = "CVE-2023-38584"
    strings:
        $a = "command_wb.cgi"
        $b = "cgi-bin"
        $c = /(A{100,}|B{100,}|C{100,}|D{100,}|E{100,}|F{100,}|[0-9a-f]{200,})/
    condition:
        all of ($a, $b) and any of ($c) and filesize < 2MB
}

Suricata IDS Rule

alert http any any -> $HOME_NET any (msg:"ET EXPLOIT Weintek cMT3000 command_wb.cgi Stack Buffer Overflow Attempt (CVE-2023-38584)"; flow:established,to_server; content:"command_wb.cgi"; http_uri; isdataat:2048,relative; pcre:"/[a-fA-F0-9]{2048,}/U"; classtype:attempted-admin; sid:2024038584; rev:1; metadata:cve CVE-2023-38584; reference:url,https://nvd.nist.gov/vuln/detail/CVE-2023-38584;)

Elastic Detection

sequence by source.ip, destination.ip with maxspan=5s
  [network where event.action == "connection_accept" and destination.port == 80 and network.protocol == "http"]
  [http where http.request.uri contains "command_wb.cgi" and length(http.request.body.bytes) > 1024]

Splunk SPL Query

index=proxy OR index=web OR index=netflow sourcetype="access_combined_wcookie" uri_path="*command_wb.cgi*"
| eval query_length = len(uri_query)
| where query_length > 1024
| stats count by src_ip, dest_ip, dest_port, uri_query, _time
| sort - _time

Wazuh OSSEC Rule

<rule id="100038" level="12">
  <decoded>.+command_wb\.cgi.*</decoded>
  <match>command_wb.cgi</match>
  <field name="url_len">>1024</field>
  <description>Weintek cMT3000 HMI command_wb.cgi buffer overflow exploitation attempt (CVE-2023-38584)</description>
  <group>web_application_attack,exploit,cve_2023_38584,</group>
  <mitre><id>T1190</id></mitre>
</rule>

Mitigation & Patch Guidance

Patch Confidence: 2/4 — CLAIMED. The vendor (CNA) has published a security bulletin (TEC23005E) and upgrade instructions, but this has not been independently confirmed by a second source. Given the absence of public exploit code, the patch claim remains plausibly valid but should be verified against the actual firmware versions on each device.

Immediate Mitigations (before patching):

1. Network segmentation: Isolate cMT3000 HMI devices from the corporate IT network and especially the internet. Place them on a dedicated OT network segment with strict firewall rules.
2. Restrict access to the Web interface: Where possible, disable the Web CGI interface entirely if not required for operations. If required, restrict access by source IP using firewall ACLs to only permit known engineering workstations.
3. Enable authentication for web access even if the bypass exists: While the vulnerability bypasses login, applying proper authentication still raises the bar and reduces the risk of opportunistic scanning.
4. Monitor for anomalous HTTP traffic: Deploy the detection rules provided in this report on network monitoring infrastructure (IDS/IPS, SIEM) to identify exploit attempts.

Patch/Upgrade Steps:

1. Download the firmware updates from Weintek's official support portal (refer to the vendor's upgrade instructions document: UM018010E).
2. Apply the appropriate OS version for each device model:
   • cMT-FHD: OS version 20210211
   • cMT-HDM: OS version 20210205
   • cMT3071, cMT3072, cMT3103, cMT3090, cMT3151: OS version 20210219
3. Follow the vendor's standard HMI firmware upgrade procedure carefully. Ensure the device is connected to a stable power source and network during the upgrade.
4. After upgrade, verify the running OS version in the device's System Information page and re-run a web interface access test to confirm normal operation.

Long-term Hardening:

1. Asset discovery: Maintain a current inventory of all HMI devices, including model, firmware version, and network location. Use this inventory to track and enforce patch compliance.
2. Vulnerability management: Integrate CVE-2023-38584 and other known HMI CVEs into the organization's vulnerability scanning and remediation workflow.
3. Defense-in-depth: Implement network intrusion detection (e.g., using the Suricata rule above) specifically for OT protocols and HMI web traffic.
4. Change management: Establish a process for testing and deploying HMI firmware updates in a staging environment before production rollout.
5. Acceptable use policy: If the Web interface is not essential, disable it. If required, place it behind a jump server or VPN with MFA.

References

1. NVD Entry for CVE-2023-38584: https://nvd.nist.gov/vuln/detail/CVE-2023-38584
2. Weintek Security Bulletin (TEC23005E): https://dl.weintek.com/public/Document/TEC/TEC23005E_cMT_Web_Security_Update.pdf
3. Weintek Upgrade Instructions (UM018010E): https://dl.weintek.com/public/Document/UM0/UM018010E_cMT_Series_OS_Update_Instructions_eng.pdf
4. CISA Known Exploited Vulnerabilities Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog
5. MITRE ATT&CK T1190 — Exploit Public-Facing Application: https://attack.mitre.org/techniques/T1190/

Threat Actor Campaigns / In-the-Wild Evidence: As of this report, CVE-2023-38584 is NOT listed in the CISA KEV catalog, and there are no known public exploit codes or confirmed in-the-wild exploitation campaigns. The EPSS score (0.01051, 61.1 percentile) places it in a moderate-risk category for near-term exploitation, meaning organizations should prioritize patching but should not assume active targeting is imminent. The primary threat vector remains generic scanning for exposed HMI web interfaces and opportunistic exploitation once public PoCs surface.