Text mode acts like Enter key is held down

Question

I recently ran updates on Xubuntu 18.04. Now if I go to a text-mode TTY, here's what happens:

1. Type anything as a username, just can't be empty.
2. Press Enter.
3. It behaves as if Enter is held down, immediately failing logon (as password is empty).
4. After 5 failures, it clears the screen and no longer acts as if Enter is held down.

If I run physlock it just immediately acts as if Enter is held and fails infinitely.

Kernel version 4.15.0-43 works fine, but 4.15.0-44 and 4.15.0-45 are broken. The recovery root shell is unaffected, even when I run login from within it.