Apps with CET support enabled do not launch

[PiMoNFeeD]

Description

I've recently updated a .NET app I had to a newer version and found out that it doesn't launch. Fast forward 2 days, I tracked down the issue to the fact that the app was upgraded from .NET 8.0 to 9.0, and testing in multiple configurations on my local machine revealed that any .NET 9.0 app simply doesn't work on my machine, unless I explicitly add <CETCompat>false</CETCompat> to the .csproj file.

Debugger is entirely useless as it only shows this:

The program '[XXX] XXX.exe' has exited with code 3221227010 (0xc0000602) 'The process aborted due to a fail fast exception.'.

If I create a console application instead, I also get this right above the aforementioned crash:

CLR: Assert failure(PID 4452 [0x00001164], Thread: 20648 [0x50a8]): !AreShadowStacksEnabled() || UseSpecialUserModeApc()
    File: D:\a\_work\1\s\src\coreclr\vm\threads.cpp:7938

That led me to #108589, where someone else had the same assert and updating their Windows helped, but they updated to the exact same build I am running from 2023, so I hardly believe this to be an issue.

Reproduction Steps

...

Expected behavior

...

Actual behavior

...

Regression?

There was no crash until CET support was forced on by default

Known Workarounds

Disabling CET support on a per-app basis

Configuration

.NET 9.0.0
Windows 10 Pro 22H2 x64 build 19045.2965, Windows Feature Experience Pack 1000.19041.1000.0

Other information

No response

[dotnet-policy-service]

Tagging subscribers to this area: @mangod9
See info in area-owners.md if you want to be subscribed.