Bun WebSocket Segmentation Fault closing invalid connection

[hakt0r]

How can we reproduce the crash?

Description

Bun crashes with a segmentation fault when attempting to close a WebSocket connection to an invalid/unreachable URL.

Minimal Reproduction

Since you insist: REPRO-REPO

import { test } from 'bun:test';

test('crash', async () => {
  const publicAddress = new URL('https://1.1.1.1:3000');
  const socket = new WebSocket(publicAddress.toString());
  // crashes -- comment this out to see the test pass
  socket.close();
});

Environment

• Bun version: 1.2.2-canary.9
• OS: Linux x64 (Kernel v6.12.9)
• CPU Features: sse42 popcnt avx avx2

Steps to Reproduce

1. Create a new file crash.test.js with the code above
2. Run bun test crash.test.js

Expected Behavior

The WebSocket should handle the invalid connection gracefully, either:

• Throwing a network error
• Failing to connect but allowing close() to be called
• Returning a rejected promise

Actual Behavior

Bun crashes with a segmentation fault at address 0x0

Relevant log output

bun test v1.2.2-canary.9 (aac951bd)

bundled.crash.test.js:
============================================================
Bun Canary v1.2.2-canary.9 (aac951bd) Linux x64
Linux Kernel v6.12.9 | glibc v2.40
CPU: sse42 popcnt avx avx2
Args: "/home/awt/Downloads/cursor-0.45.8-build-250201b44xw1x2k-x86_64.AppImage" "test" "bundled.crash.test.js"
Features: WebSocket jsc 
Elapsed: 16ms | User: 8ms | Sys: 21ms
RSS: 1.07GB | Peak: 40.28MB | Commit: 1.07GB | Faults: 0

panic(main thread): Segmentation fault at address 0x0
oh no: Bun has crashed. This indicates a bug in Bun, not your code.

To send a redacted crash report to Bun's team,
please file a GitHub issue using the link below:

 https://bun.report/1.2.2/lt2aac951bAwggEo2rnoE+5+P27l24DigkxkE_g2qr9Dghir9Dg2qr9Dmsoj9Duk6x8EA2AA

Stack Trace (bun.report)

bun.report comes up with internal server error

https://bun.report/1.2.2/lt2aac951bAwggEo2rnoE+5+P27l24DigkxkE_g2qr9Dghir9Dg2qr9Dmsoj9Duk6x8EA2AA

[Jarred-Sumner]

I haven’t been able to reproduce this on Linux or macOS. We will have address sanitizer working early this week and hopefully it will reproduce there.