Critical Authentication Bypass Flaw in Moxa Ethernet Switches Exposes Industrial Networks

Critical Authentication Bypass in Moxa Ethernet Switches Discovered

The Spanish National Cybersecurity Institute (INCIBE) has issued an urgent alert regarding a severe authentication bypass vulnerability affecting Moxa Ethernet switches. The flaw, identified on February 4, 2026, allows unauthenticated remote attackers to gain unauthorized access to affected devices, posing significant risks to industrial control systems (ICS) and critical infrastructure.

Technical Details of the Vulnerability

While specific CVE identifiers have not been disclosed in the initial advisory, the vulnerability stems from a lack of proper authentication mechanisms in certain Moxa Ethernet switch models. Attackers exploiting this flaw could:

• Bypass authentication controls to access administrative interfaces
• Execute arbitrary commands with elevated privileges
• Disrupt network operations in industrial environments
• Move laterally within OT/ICS networks

The affected devices are commonly deployed in manufacturing, energy, transportation, and water treatment facilities, where network segmentation and access control are critical for operational security.

Impact Analysis

Successful exploitation of this vulnerability could lead to:

• Unauthorized configuration changes in industrial switches
• Network traffic interception or manipulation
• Denial-of-service (DoS) conditions in critical operational networks
• Potential safety risks in environments where networked devices control physical processes

INCIBE’s advisory emphasizes that no user interaction is required for exploitation, increasing the likelihood of automated attacks or mass scanning by threat actors.

Recommended Actions for Security Teams

INCIBE and Moxa urge organizations to take immediate steps to mitigate risks:

1. Identify affected Moxa switches in your environment using asset inventory tools
2. Apply vendor-supplied patches as soon as they become available (monitor Moxa’s security advisories for updates)
3. Implement network segmentation to isolate vulnerable devices from critical systems
4. Enforce strict access controls, including:
   • Restricting administrative interfaces to trusted IP ranges
   • Disabling unnecessary remote management protocols
   • Enabling multi-factor authentication (MFA) where supported
5. Monitor network traffic for anomalous activity targeting Ethernet switches
6. Review logs for signs of unauthorized access attempts

Organizations relying on Moxa Ethernet switches in industrial environments should prioritize this vulnerability due to its high severity and ease of exploitation. Further technical details, including affected firmware versions and CVE assignments, are expected to be released by Moxa in the coming days.

For real-time updates, security teams are advised to follow INCIBE’s official advisory.