id summary reporter owner description type status component version resolution keywords cc guest host 14659 Emulated COM1 IRQ reported as 0 to hosts on VBox 5.0.6 Peter Palúch "Greetings, I am running Debian Jessie (AMD64) on my host machines. After upgrading to VirtualBox 5.0.6, my guest OSes started reporting the IRQ of the emulated serial port 1 (COM1 / ttyS0) as 0, see attached screenshots. As a result, Windows hosts are unable to use the serial port - they claim an error that ""the device cannot start (code 10)"". Linux guests are more lenient and while they also report the IRQ of the serial port 1 to be 0, they nonetheless appear to be able to use it. Reverting back to VBox 5.0.4 solves the problem entirely, so this appears to be a regression in the 5.0.6 release. I have been able to reproduce this problem reliably on 19 machines (I have discovered it after upgrading an entire classroom ;) ). Thanks for looking into this issue! Best regards, Peter" defect closed uart VirtualBox 5.0.6 fixed all Linux