Blast-RADIUS Attack: A Critical Vulnerability in RADIUS Authentication. Here is a quick look.


Blast-RADIUS Attack: A Critical Vulnerability in RADIUS Authentication. Here is a quick look.

In a shocking revelation, security researchers have uncovered a critical vulnerability in the Remote Authentication Dial-In User Service (RADIUS) protocol. This ubiquitous authentication scheme, which has been in use for over three decades, is now at risk due to a newly discovered attack known as Blast-RADIUS.



RADIUS, originally developed in 1991 by Livingston Enterprises, remains a cornerstone of lightweight authentication. It facilitates seamless interactions between network devices (such as routers, switches, and access points) and a central RADIUS server. This server acts as the gatekeeper for user authentication and access policies across various scenarios, including:

  • VPN access
  • DSL and Fiber to the Home connections provided by ISPs
  • Wi-Fi and 802.1X authentication
  • Cellular roaming (2G, 3G, and now 5G)
  • Authentication over private APNs for connecting mobile devices to enterprise networks
  • Critical infrastructure management devices
  • Eduroam and OpenRoaming Wi-Fi

Despite its age, RADIUS continues to play a pivotal role in managing client-server interactions across diverse environments.

The MD5 Quandary

Here lies the crux of the issue: RADIUS has long relied on an improvised use of the MD5 hash function for authentication. MD5, created in 1991 and adopted by the Internet Engineering Task Force (IETF) in 1992, was once popular for generating fixed-length message digests. However, its design flaws have become increasingly apparent over time.

A cryptographic hash function should make it computationally impossible for an attacker to find two inputs that map to the same output. Unfortunately, MD5’s susceptibility to collisions—where distinct inputs produce identical outputs—poses a serious threat. Blast-RADIUS capitalizes on this weakness.

The Blast-RADIUS Attack

The Blast-RADIUS attack leverages two key elements:

  1. Protocol Vulnerability (CVE-2024-3596): Exploiting a flaw in the RADIUS protocol, attackers gain access to RADIUS traffic. They can then manipulate server responses and inject arbitrary protocol attributes. This manipulation allows them to bypass authentication and gain admin privileges on RADIUS devices without brute force or credential theft.
  2. MD5 Collision Attack: By exploiting MD5 collisions, attackers can create distinct inputs that yield the same hash value. In the context of RADIUS, this means they can forge authentication responses, compromising the integrity of the entire system.

Impact and Mitigation of Blast-RADIUS

The implications are far-reaching. Blast-RADIUS jeopardizes industrial controllers, telecommunications services, ISPs, and enterprise networks. Organizations must take immediate action to safeguard their RADIUS implementations:

  • Upgrade to a Secure Hash Function: Migrate away from MD5 to a more robust hash function (e.g., SHA-256).
  • Implement Network Segmentation: Isolate RADIUS servers from other critical infrastructure.
  • Monitor Traffic: Detect anomalous behavior and potential attacks.
  • Stay Informed: Keep abreast of security advisories and patches.


The Blast-RADIUS attack serves as a stark reminder that even well-established protocols can harbor vulnerabilities. As we navigate this evolving threat landscape, vigilance and proactive security measures are paramount. Let’s fortify our networks and protect the digital realm against malicious actors

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