CVE-2022-40224

What it actually does

CVE-2022-40224 is a network-exploitable denial-of-service vulnerability in the web server functionality of Moxa SDS-3008 Series Industrial Ethernet Switch firmware version 2.1. A specially crafted HTTP request header can cause the device’s embedded web service, and potentially device management functionality, to become unavailable. The CVSS vector indicates exploitation is remote, low complexity, requires no authentication, and does not require user interaction, with impact limited to availability rather than confidentiality or integrity.

Why it matters to the business

Successful exploitation can disrupt management access to affected industrial Ethernet switches and may impair operational visibility or control in industrial networks. In environments where these switches support production, automation, safety, or monitoring networks, even a management-plane denial of service can delay troubleshooting, increase operational risk, and contribute to network instability. The relatively high EPSS score and public exploit availability increase the likelihood of internet- or OT-network scanning and opportunistic exploitation, even though the issue is not currently listed in CISA KEV and is not known to be used in ransomware campaigns.

How an attack unfolds

An attacker first identifies an exposed Moxa SDS-3008 Series switch with its web management interface reachable over the network. Because exploitation does not require authentication, the attacker can send a crafted HTTP request containing malformed or oversized header content directly to the embedded web server. The vulnerable firmware mishandles the HTTP header and enters a denial-of-service condition, causing the web server or affected management functions to stop responding. The attacker may repeat the request to maintain the outage or trigger it again after the device or service is restarted. In an OT environment, this may be used as a disruptive action, a distraction during other activity, or a way to hinder defenders and operators from managing network infrastructure.

How to fix it

Upgrade affected Moxa SDS-3008 Series and SDS-3008-T devices from vulnerable firmware version 2.1 to a vendor-provided fixed firmware release if available from Moxa support or the product download portal. If an explicit fixed version is not available in the provided data, treat firmware 2.1 as vulnerable and verify remediation guidance directly with Moxa. Until patched, restrict access to the web management interface using dedicated management VLANs, firewall rules, ACLs, VPN-only administration, and allowlists for trusted engineering workstations. Disable web management if not required, or prefer more tightly controlled management channels where feasible. Avoid exposing OT switch management interfaces to the internet or broad enterprise networks. Ensure recovery procedures exist, including tested device reboot/replacement processes and configuration backups.

How to confirm the fix worked

Confirm the inventory of Moxa SDS-3008 and SDS-3008-T devices and verify firmware versions through the device UI, CLI, SNMP, asset management tooling, or vendor management software. Devices running firmware version 2.1 should be considered exposed unless upgraded or isolated. Validate that web management ports are not reachable from untrusted networks by performing controlled network scans from enterprise, DMZ, remote access, and internet-adjacent segments. After remediation, confirm the device remains stable under normal management traffic and that access controls block unauthorized HTTP/HTTPS requests. Avoid destructive proof-of-concept testing against production OT devices unless approved and performed in a maintenance window.

Typical attack path

1. Scan for Moxa SDS-3008 Series switches or embedded web management interfaces exposed on HTTP/HTTPS management ports.
2. Fingerprint the target device or firmware through banners, login pages, web assets, or network behavior.
3. Send a specially crafted HTTP request with a malformed header to the device web server.
4. Trigger the denial-of-service condition in the embedded web server or management interface.
5. Optionally repeat the request to sustain the outage or re-trigger the failure after recovery.

How to detect it

Investigate whether affected switch management interfaces received unusual or malformed HTTP traffic shortly before a management outage, device reboot, watchdog reset, or loss of web UI responsiveness. Useful sources include firewall logs, IDS/IPS alerts, switch management logs if available, NetFlow/IPFIX, packet captures, OT monitoring platforms, remote-access/VPN logs, and centralized syslog from network infrastructure. Look for unauthenticated HTTP requests to Moxa switch management IPs with unusually long headers, malformed header names or values, repeated requests immediately followed by connection resets, HTTP 400/500 responses, TCP resets, or gaps in device telemetry. Correlate suspected requests with alarms for device unavailability, SNMP polling failures, web login page downtime, or operator reports of failed management access. Because this is a denial-of-service issue rather than code execution, host-based artifacts may be limited; network evidence and uptime/reboot timelines are typically the most useful forensic sources.

• HTTP requests to Moxa SDS-3008 management interface with unusually large HTTP header fields
• HTTP requests to Moxa SDS-3008 management interface with malformed header names or malformed header values
• Repeated unauthenticated HTTP requests immediately preceding loss of web management access
• HTTP 400 responses from Moxa SDS-3008 web management interface followed by connection reset
• HTTP 500 responses from Moxa SDS-3008 web management interface followed by connection reset
• TCP RST traffic from Moxa SDS-3008 management IP immediately after HTTP header processing
• SNMP polling failure for Moxa SDS-3008 immediately after inbound HTTP request burst
• Loss of web UI responsiveness on Moxa SDS-3008 firmware 2.1 after crafted HTTP request traffic
• Inbound HTTP traffic to exposed Moxa SDS-3008 management interface from untrusted source networks

What your security team should do

• Prioritize identifying all Moxa SDS-3008 and SDS-3008-T switches, especially those in production OT networks or reachable from routed enterprise networks.
• Check firmware versions and plan upgrade or vendor-supported remediation for any device running SDS-3008 Series firmware 2.1.
• Immediately restrict HTTP/HTTPS management access to trusted administrative networks and remove any internet exposure.
• Monitor for abnormal HTTP requests to switch management interfaces, repeated connection attempts, and sudden loss of web management availability.
• Review firewall, VPN, and remote-access paths to ensure attackers cannot reach industrial switch management services from untrusted zones.
• Maintain offline configuration backups and operational recovery procedures for affected switches to reduce outage duration.
• Because exploit code is available and EPSS is elevated, treat unpatched reachable devices as high-priority even though the vulnerability is not currently in CISA KEV.