In Tcl_ZlibInflate of generic/tclZlib.c there is this error block:

	if ((stream.avail_in == 0) && (stream.avail_out > 0)) {
	    e = Z_STREAM_ERROR;
	    goto error;
	}

I believe that needs to call inflateEnd(&stream) before the goto to avoid leaking zlib memory structures. This leak would only occur if you are trying to decompress corrupted/incomplete data a lot.

Fixed on trunk via check-in [513c7ae3fcc2b76a].  There is no easy way to
automatically test this; however, I manually verified it by observing the
process memory usage with and without the fix (i.e. without the fix, the
memory usage kept growing).

Is there perhaps also a leak in this error block earlier in that function?

    if (headerPtr) {
	e = inflateGetHeader(&stream, headerPtr);
	if (e != Z_OK) {
	    goto error;
	}
    }

I think that should also call inflateEnd(&stream) prior to the goto?