What Are Serial-to-IP Converters and Why Do They Matter?
Serial-to-IP converters — also referred to as serial device servers — are hardware components that connect legacy serial equipment to modern Ethernet/IP networks. Their primary purpose is to allow older industrial control systems (ICS) and other operational technology (OT) devices to communicate over contemporary network infrastructure. Because of this bridging function, they are deeply embedded in industries ranging from manufacturing and energy to healthcare and transportation.
Major vendors in this space include Moxa, Digi, Advantech, Perle, Lantronix, and Silex, some of which have reported deploying millions of units globally. A search on Shodan reveals nearly 20,000 internet-exposed serial device servers worldwide — a significant and concerning attack surface.
Forescout Uncovers 20 New Vulnerabilities
Researchers at Forescout Technologies, a network security and threat detection company, conducted an in-depth analysis of serial-to-IP converters, focusing specifically on devices manufactured by Silex and Lantronix. Their investigation led to the discovery of 20 new vulnerabilities spanning both vendors' product lines. Forescout has collectively labeled these weaknesses BRIDGE:BREAK.
The vulnerabilities span a wide range of severity and exploitation techniques, including:
- OS command injection and remote code execution (RCE)
- Firmware tampering and delivery of malicious firmware
- Denial-of-service (DoS) attacks
- Full device takeover
- Arbitrary file upload
- Authentication bypass
- Information disclosure
Critically, some of these flaws can be exploited without authentication, dramatically lowering the barrier for opportunistic attackers.
How Attackers Could Exploit These Devices
Beyond internet-exposed units, attackers could also target serial-to-IP converters sitting on internal networks by first pivoting through misconfigured or compromised edge devices such as routers and firewalls. Forescout researchers noted that open-source intelligence (OSINT) makes reconnaissance particularly straightforward.
"Using open-source intelligence (OSINT), attackers can find details about some of these devices, including internal IP addresses, model and vendor names, and photographs from electrical substations, water treatment plants, and other critical infrastructure environments," the Forescout researchers explained.
The research team demonstrated real-world attack scenarios to illustrate the potential consequences of successful exploitation.
Scenario 1: Data Manipulation in Industrial and Healthcare Settings
In one demonstrated scenario, an attacker exploits BRIDGE:BREAK vulnerabilities to tamper with sensor data. By manipulating readings sent back from environmental or medical sensors, the attacker could effectively conceal dangerous conditions that would otherwise trigger human intervention — a particularly alarming prospect in hospitals or industrial facilities where automated alerts are relied upon for safety.
Scenario 2: Weaponized Firmware in a Healthcare Environment
In a second scenario, Forescout described how an extortion group or a state-sponsored threat actor could push malicious firmware to serial device servers in a hospital or clinical setting. Once that firmware activates, the converters stop responding on the network entirely. According to the researchers, the cascading consequences could include:
- Analyzers ceasing to report results to laboratory information systems, causing processing backlogs
- Surgical lighting controllers becoming unresponsive to remote commands
- Infusion pump calibration and certification workflows being halted
- Telemetry from environmental sensors being interrupted
- Patient monitors losing network connectivity
These outcomes highlight just how high the stakes are when industrial-grade hardware intersects with patient safety infrastructure.
Vendor Response and Patches
Both Lantronix and Silex were notified of the vulnerabilities through coordinated disclosure. Each vendor has since released patches to address the identified flaws. The U.S. Cybersecurity and Infrastructure Security Agency (CISA) published a formal advisory detailing the Lantronix vulnerabilities, while Silex issued its own security advisory on its official website. Organizations relying on devices from either vendor are strongly urged to apply available updates without delay.
A History of Targeting in the Wild
The risks associated with serial-to-IP converters are not merely theoretical. These devices have already been targeted by real-world threat actors. They played a role in the 2015 Ukraine energy attack carried out by Russian hackers — one of the first documented cyberattacks to cause a physical power outage — and have more recently appeared as targets in attacks against energy facilities in Poland.
This track record underscores why organizations cannot afford to treat serial device server security as a low-priority concern. The combination of internet exposure, outdated authentication mechanisms, and deep integration into safety-critical systems makes these devices an attractive target for both cybercriminals and nation-state actors.
Full Research Report Forthcoming
Forescout is scheduled to publish a comprehensive report detailing the BRIDGE:BREAK vulnerability set on Tuesday, April 21. The report is expected to provide deeper technical analysis of the individual CVEs and guidance for defenders seeking to harden their environments against exploitation.
Recommended Mitigations
While specific patch guidance will come from the vendors and CISA, organizations should consider taking the following general steps to reduce their exposure:
- Audit all serial-to-IP converters in the environment and confirm they are not directly internet-accessible
- Apply vendor-issued firmware patches immediately upon availability
- Segment serial device servers from the broader network using firewalls and VLANs
- Monitor network traffic to and from these devices for anomalous behavior
- Disable any unnecessary services or remote management interfaces on the devices
- Use OSINT searches such as Shodan to identify any unintentionally exposed assets
Given that serial-to-IP converters are present in sectors as varied as telecoms, retail, utilities, and transportation — in addition to OT and healthcare — the scope of organizations that should act on this research is broad. The BRIDGE:BREAK findings serve as a timely reminder that legacy infrastructure integration points can carry modern, high-severity security risk.
Source: SecurityWeek