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[Windows] Null pointer crash in HostWindowPopup::UpdatePosition (regression in 3.47.0) #191478
Description
I recently upgraded from flutter 3.44.9 to flutter 3.47.0 and noticed that the upgrade introduced a new crash on windows. This surfaced as a EXCEPTION_ACCESS_VIOLATION_READ crash in my application.
I was able to trace the issue to HostWindowPopup and have proposed a fix with this change. #191479
Steps to reproduce
- Windows desktop app embedding a native HWND-backed platform view (
webview_windows, in my case) in a page. - Navigate away, disposing that page.
- Crashes 100% of the time on 3.47.0.
Expected results
App keeps running after navigating away.
Actual results
Crash in flutter_windows.dll:
AV.Dereference: NullPtr
AV.Type: Read
flutter_windows!InternalFlutterWindows_WindowManager_UpdatePopupPosition+0x28ddcc
mov rax,qword ptr [rcx] ; rcx = 0
Bisected: no crash on 3.44.9 (engine b9499e4c25, HostWindowPopup didn't exist), crashes 100% on 3.47.0 (engine 59d54a2b28).
Code sample
Code sample. I haven't isolated a minimal repro without the plugin. The linked PR includes an engine-level unit test (`PopupWindowHandlesNullPositionCallback`) that reproduces the defect directly with no app code — it crashes the test binary unpatched, passes with the fix.
class WebViewPageWindowsState extends State<WebViewPageWindows> {
final WebviewController webViewController = WebviewController();
@override
Widget build(BuildContext context) => Stack(
children: [
Webview(webViewController),
if (firstLoad) const CircularProgressIndicator(),
],
);
@override
void dispose() {
webViewController.dispose();
super.dispose();
}
}
void _goToNativeLogin() {
BlazeSession().clearCookies();
if (context.mounted) context.go("/login"); // disposes the page above
}Screenshots or Video
Screenshots / Video demonstration
[Upload media here]
Logs
Logs
[Paste your logs here]Flutter Doctor output
Doctor output
PS C:\Users\kiran\Development\blazetrade-flutter> flutter doctor -v
[!] Flutter (Channel [user-branch], 3.47.0, on Microsoft Windows [Version 10.0.26200.9168], locale en-US) [343ms]
! Flutter version 3.47.0 on channel [user-branch] at C:\src\flutter
Currently on an unknown channel. Run `flutter channel` to switch to an official channel.
If that doesn't fix the issue, try deleting the 'bin/cache/flutter.version.json' file in your Flutter SDK
directory and then reinstall Flutter by following instructions at https://flutter.dev/setup.
• Upstream repository https://github.com/flutter/flutter.git
• Framework revision 4cf2416426 (10 days ago), 2026-08-11 11:53:49 -0700
• Engine revision 5f77625673
• Dart version 3.13.0
• DevTools version 2.60.0
• Feature flags: enable-web, enable-linux-desktop, enable-macos-desktop, enable-windows-desktop, enable-android,
enable-ios, cli-animations, enable-native-assets, enable-record-use, enable-swift-package-manager,
omit-legacy-version-file, enable-lldb-debugging, enable-uiscene-migration, enable-riscv64
• If those were intentional, you can disregard the above warnings; however it is recommended to use "git" directly
to perform update checks and upgrades.
[✓] Windows Version (Windows 11 or higher, 25H2, 2009) [728ms]
[✗] Android toolchain - develop for Android devices [131ms]
✗ Unable to locate Android SDK.
Install Android Studio from: https://developer.android.com/studio/index.html
On first launch it will assist you in installing the Android SDK components.
(or visit https://flutter.dev/to/windows-android-setup for detailed instructions).
If the Android SDK has been installed to a custom location, please use
`flutter config --android-sdk` to update to that location.
[✓] Chrome - develop for the web [117ms]
• Chrome at C:\Program Files\Google\Chrome\Application\chrome.exe
[✓] Visual Studio - develop Windows apps (Visual Studio Build Tools 2026 18.9.0) [115ms]
• Visual Studio at C:\Program Files (x86)\Microsoft Visual Studio\18\BuildTools
• Visual Studio Build Tools 2026 version 18.9.12105.275
• Windows 10 SDK version 10.0.26100.0
[✓] Connected device (3 available) [119ms]
• Windows (desktop) • windows • windows-x64 • Microsoft Windows [Version 10.0.26200.9168]
• Chrome (web) • chrome • web-javascript • Google Chrome 151.0.7922.138
• Edge (web) • edge • web-javascript • Microsoft Edge 151.0.4129.93
[✓] Network resources [309ms]
• All expected network resources are available.
! Doctor found issues in 2 categories.```
</details>
Activity
mbcorona commentedon Aug 21, 2026
Hi @kryali, thanks for the bisection and for the fix PR #191479
Routing to the Windows team for evaluation.
[windows] Fix null-deref in HostWindowPopup::UpdatePosition (Fixes fl…