A newly identified vulnerability, dubbed Blast-RADIUS, presents a severe security threat to the RADIUS protocol, a fundamental component for authentication, authorization, and accounting (AAA) in enterprise and telecommunication networks. The vulnerability allows a man-in-the-middle attacker to forge a valid protocol accept message in response to a failed authentication request. This forged message can grant the attacker unauthorized access to network devices and services without the need to guess passwords or shared secrets, bypassing traditional security measures and potentially leading to significant security breaches.
Blast-RADIUS affects all RADIUS implementations that use non-EAP authentication methods over UDP, making it a widespread and critical issue. The vulnerability impacts a broad spectrum of applications, including enterprise network access to switches and routing infrastructure, VPN access, ISP services for DSL and FTTH, 802.1X and Wi-Fi authentication, 2G and 3G cellular roaming, 5G Data Network Name (DNN) authentication, mobile Wi-Fi offload with SIM card-based authentication, private APN authentication, and access to critical infrastructure. It also affects educational and roaming Wi-Fi consortia like Eduroam and OpenRoaming, further underscoring the extensive reach of this vulnerability.
The root of the Blast-RADIUS vulnerability lies in the RADIUS protocol’s reliance on outdated cryptographic mechanisms. Predating modern cryptographic standards, RADIUS typically lacks proper encryption and authentication. The protocol attempts to authenticate server responses using an ad hoc construction based on the MD5 hash function and a fixed shared secret between a client and server. The Blast-RADIUS attack combines a novel protocol vulnerability with an MD5 chosen-prefix collision attack, alongside new speed and space improvements. By injecting a malicious attribute into a request, the attacker causes a collision between the valid server response’s authentication information and the attacker’s forged response. This allows the attacker to turn a reject into an accept and add arbitrary protocol attributes, thereby gaining unauthorized access.
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