Crash in libquic.dylib when app is backgrounded and issues an HTTP/3 request on iOS 26

Title / Summary

Crash in libquic.dylib when app is backgrounded and issues an HTTP/3 request

Description

On iOS 26, the app crashes inside libquic.dylib while performing a network request using HTTP/3 (QUIC) after the app has moved to the background. The crash happens within low-level QUIC / libquic internals.

Reproduction Steps

  1. Launch the app, perform normal operations.
  2. Background the app (press home / switch away).
  3. While in background, trigger a network request that uses HTTP/3 / QUIC.
  4. Observe that the app crashes (stack trace pointing into libquic.dylib).

Expected Behavior

The HTTP/3 request in background should either be handled gracefully (fail or complete) without causing a crash; the app must not be terminated due to internal libquic failures.

Actual Behavior

The app crashes with signals/exceptions coming from libquic.dylib (in the QUIC / packet building / encryption / key state logic) when a HTTP/3 request is made in background.

Environment / Device Information

• OS: iOS 26

• Device: iPhone 13 Pro Max

• Network environment: (Wi-Fi / Cellular)

• HTTP/3 support: enabled in URLSession / Network framework

Stack Trace:

Answered by DTS Engineer in 860503022

Thanks for the crash report.

We collected the crash logs from users online.

So, does that mean that you can’t reproduce this yourself? Because in your original post you had “Reproduction Steps”, which suggests that this is something you can reproduce.


Based on thread 8, it looks like you’re using a third-party crash reporter. That makes things difficult, as I explain in Implementing Your Own Crash Reporter. My advice is that you remove this crash reporter from your app and try to get a Apple crash report for this crash.

Still, it’s probably worthwhile filing a bug with the info that you currently have. Please do that, and then post your bug number here.

Share and Enjoy

Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Please post a full Apple crash report, per the advice in Posting a Crash Report

IMPORTANT It sounds like you can reproduce this, which is great. In that case you should be able to post a JSON-format crash report (.ips), which is what I’d really like to see.

Share and Enjoy

Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Thanks for the crash report.

We collected the crash logs from users online.

So, does that mean that you can’t reproduce this yourself? Because in your original post you had “Reproduction Steps”, which suggests that this is something you can reproduce.


Based on thread 8, it looks like you’re using a third-party crash reporter. That makes things difficult, as I explain in Implementing Your Own Crash Reporter. My advice is that you remove this crash reporter from your app and try to get a Apple crash report for this crash.

Still, it’s probably worthwhile filing a bug with the info that you currently have. Please do that, and then post your bug number here.

Share and Enjoy

Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Crash in libquic.dylib when app is backgrounded and issues an HTTP/3 request on iOS 26
 
 
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