The Cybersecurity and Infrastructure Security Agency (CISA) has released a critical security alert identifying a significant vulnerability in railway End-of-Train and Head-of-Train communication systems that could potentially allow attackers to issue unauthorized brake commands to trains across the United States transportation network.
Critical Flaw in End-of-Train Communication
The vulnerability, designated CVE-2025-1727 with alert code ICSA-25-191-10, affects the remote linking protocol used between End-of-Train (EoT) and Head-of-Train (HoT) devices, commonly known as FRED (Flashing Rear End Device) systems.
Cybersecurity researchers Neil Smith and Eric Reuter discovered the flaw, which has been assigned a CVSS v4 base score of 7.2, indicating a high-severity risk to critical infrastructure.
The vulnerability stems from weak authentication mechanisms classified as CWE-1390 in the protocol’s design. The system relies on a BCH checksum for packet creation during radio frequency communication between train components.
According to CISA’s technical analysis, malicious actors could exploit this weakness using software-defined radio technology to craft legitimate-appearing EoT and HoT packets, effectively spoofing communication between train systems.
Potential for Unauthorized Brake Commands
The security flaw presents serious operational and safety risks to the U.S. transportation sector.
Successful exploitation could enable attackers to transmit unauthorized brake control commands directly to end-of-train devices, potentially causing sudden train stoppages that could disrupt freight and passenger operations nationwide.
More concerning, the vulnerability could potentially be leveraged to induce brake system failures, creating significant safety hazards.
The CVSS vector string (AV:A/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:H/SC:N/SI:H/SA:H) indicates that while the attack requires adjacent network access, it has low complexity requirements and needs no user interaction, making it relatively straightforward for determined attackers to exploit.
The vulnerability affects all versions of the End-of-Train and Head-of-Train remote linking protocol currently deployed across the industry.
Industry Pursuing New Standards to Address Vulnerability
The Association of American Railroads (AAR) has acknowledged the security concern and is actively developing new equipment and protocols to replace traditional EoT and HoT systems.
The Railroad Electronics Standards Committee (RESC), which maintains the affected protocol, is coordinating with major industry manufacturers, including Hitachi Rail STS USA, Wabtec, and Siemens, to investigate comprehensive mitigation strategies.
CISA recommends immediate defensive measures, including network isolation, firewall implementation, and restricting internet accessibility for control system devices.
Organizations should implement Virtual Private Networks (VPNs) for necessary remote access while ensuring systems remain updated.
The agency emphasizes that no known public exploitation has been reported, and the vulnerability cannot be exploited remotely, requiring physical proximity to railway systems for successful attacks.
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