CVE-2022-33178 - How a RADIUS Bug in Brocade Fabric OS Let Attackers Run Code on Switches

When we talk about network security, the words "remote code execution" (RCE) are chilling—especially when the target is your core switches. In this post, we dive deep into CVE-2022-33178, a serious vulnerability that was discovered in the RADIUS authentication module of Brocade Fabric OS (FOS) versions before 9.. I’ll walk you through how it works, why it’s dangerous, the exploit path, and show simple code snippets that help you understand the danger.

What Is CVE-2022-33178 All About?

Brocade switches run an OS called Fabric OS, widely used in SAN (Storage Area Network) environments—think data centers and enterprise IT. If attackers can run their own code on these switches, they can intercept, redirect, or stop your most sensitive data flows.

CVE-2022-33178 exploits a vulnerability in the way Brocade Fabric OS handles RADIUS (Remote Authentication Dial-In User Service) authentication—a common protocol for network login. When a remote attacker sends specially crafted packets to the RADIUS service of a vulnerable switch, the input can trigger a buffer overflow, allowing the attacker to take control of the system.

### Official Advisory & References

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How Does the Exploit Work?

This vulnerability boils down to how Fabric OS parses certain attributes in RADIUS responses. If an attacker controls a malicious RADIUS server or can intercept and spoof RADIUS responses, they can send overlong fields that overflow the allocated buffer in the Brocade code, overwriting the execution flow.

Technical Snippet: Vulnerable Function (Pseudo C Code)

Here’s a simplified code snippet to help understand the problem.

void process_radius_response(char* radius_response) {
    char buffer[256];
    // Vulnerable: No bounds checking on the length of radius_response!
    strcpy(buffer, radius_response);  
    // If 'radius_response' is >256 bytes, buffer overflow occurs here
}

If a RADIUS response attribute (for example, the "Reply-Message" field) exceeds the expected size, it spills over into the memory after buffer—potentially overwriting return addresses and other critical structures.

How Attackers Might Use This

Let’s say an attacker has the ability to act as a fake RADIUS server (possibly by ARP spoofing or DNS manipulation), or can control the RADIUS traffic. They can craft a payload with shellcode embedded in it:

payload = b"A" * 264   # Overflow the buffer, up to saved return pointer
payload += b"\xef\xbe\xad\xde"  # Overwrite return address with attacker-controlled address (little endian)
payload += shellcode   # Actual shellcode to run
send_radius_response(payload)

How Bad Is It?

- Remote Code Execution: Full control over Fabric OS—install malware, exfiltrate data, pivot to other systems.
- No Authentication Needed: The attack happens before any authentication, as it exploits the authentication module itself.
- Hard To Detect: If your logging and monitoring don’t cover authentication module crashes or strange behavior, attackers can be in and out without noise.

Mitigation Steps

1. Upgrade Immediately: Brocade addressed this bug in Fabric OS 9. and later. Update your switches now.

Disable RADIUS: If you can’t upgrade immediately, turn off RADIUS authentication temporarily.

3. Monitor Logs: Watch for authentication module crashes, reboots, or strange logins from your RADIUS systems.

Final Word

CVE-2022-33178 is a critical reminder: always keep your firmware up to date, especially for core infrastructure exposed to authentication protocols. This bug allowed attackers to run arbitrary code just by sending a malicious RADIUS response—no need for valid credentials. If you use Brocade switches, double-check your version and patch status today.

Timeline

Published on: 10/25/2022 21:15:00 UTC
Last modified on: 03/02/2023 16:06:00 UTC