RADIUS/UDP vulnerable to improved MD5 collision attack

This post details a new 'Blast-RADIUS' attack that exploits MD5 collisions in the RADIUS Response Authenticator to achieve Man-in-the-Middle (MitM) unauthorized administrative access to network devices. The attack targets RADIUS/UDP authentication modes (PAP, CHAP, MS-CHAP) by forging the Response Authenticator, which is based on an ad hoc MD5 construction. The post explains the cryptographic weaknesses of MD5 in this context, including length extension attacks and identical prefix collisions, and discusses the implications for network security. It also highlights the lack of widespread adoption of RADIUS over TLS (RADSEC) and provides an overview of mitigations for network operators.