https://www.blastradius.fail/
Blast-RADIUS is a vulnerability that affects the RADIUS protocol. RADIUS is a very common protocol used for authentication, authorization, and accounting (AAA) for networked devices on enterprise and telecommunication networks.
What can the attacker do?
The Blast-RADIUS attack allows a man-in-the-middle attacker between the RADIUS client and server to forge a valid protocol accept message in response to a failed authentication request. This forgery could give the attacker access to network devices and services without the attacker guessing or brute forcing passwords or shared secrets. The attacker does not learn user credentials.
Who is affected?
Blast-RADIUS is a protocol vulnerability, and thus affects all RADIUS implementations using non-EAP authentication methods over UDP.
System administrators of networks using RADIUS should check with vendors for a patch against this vulnerability, and follow best practices for RADIUS configuration as discussed below. There is nothing that end users can do on their own to protect against this attack.
RADIUS is used in a wide variety of applications, including in enterprise networks to authenticate access to switches and other routing infrastructure, for VPN access, by ISPs for DSL and FTTH (Fiber to the Home), in 802.1X and Wi-Fi authentication, 2G and 3G cellular roaming and 5G DNN (Data Network Name) authentication, mobile Wi-Fi offload with SIM card-based authentication, private APN authentication, to authenticate access to critical infrastructure, and in the Eduroam and OpenRoaming wifi consortia.
What is the vulnerability?
The RADIUS protocol predates modern cryptographic guarantees and is typically unencrypted and unauthenticated. However, the protocol does attempt 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.
Our attack combines a novel protocol vulnerability with an MD5 chosen-prefix collision attack and several new speed and space improvements. The attacker injects a malicious attribute into a request that causes a collision between the authentication information in the valid server response and the attacker’s desired forgery. This allows the attacker to turn a reject into an accept, and add arbitrary protocol attributes.
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