Steve, I added 3.5 because the crash involved ucrtbase.dll. I'll remove it for now since the problem is only confirmed in 3.6.

Offset 0x3bd9e in 32-bit ucrtbase.dll is in wdupenv_s [1]. It's probably from calling new_spawnve in pydev_monkey.py, as shown in the faulthandler output. I don't use PyCharm, so I can't confirm this, but we know wdupenv_s is called by the CRT's wspawnve function. For example:

    >>> os.spawnve(os.P_WAIT, sys.executable, ['python', '-V'], os.environ)

    Breakpoint 0 hit
    eax=01b412b0 ebx=00000000 ecx=01b41280 edx=01b412b2 esi=01b41280 edi=00000000
    eip=7672bd9e esp=013ef368 ebp=013ef380 iopl=0         nv up ei pl nz na po nc
    cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00000202
    ucrtbase!wdupenv_s+0x18e:
    7672bd9e 668b08          mov     cx,word ptr [eax]        ds:002b:01b412b0=0070
    0:000> kc 7
    ucrtbase!wdupenv_s
    ucrtbase!wsearchenv_s
    ucrtbase!wspawnlpe
    ucrtbase!wspawnlpe
    ucrtbase!wspawnve
    python36!os_spawnve_impl
    python36!os_spawnve

[1]: https://msdn.microsoft.com/en-us/library/ms175774.aspx