Flight Crew Air Transport Pilot (ATP)
ATC Issue All Types; Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude
Flight Crew FLC complied w / Automation / Advisory
Procedure; Human Factors
On arrival into BOS (QUABN 3 RNAV); we were given a clearance of UROWT at 11;000 feet then descend via the QUABN 3; 4R transition into BOS. Between UROWT and QUABN; ATC gave us a heads up that a VFR aircraft was at our 1 O'clock position; opposite direction; at 6;000 feet climbing to 12;500 feet.  We began to look for the traffic that we had on TCAS; [but] before we could locate it; we got a climbing TCAS RA with a vertical speed of about 2;000 fpm; which I responded to immediately; and the captain notified ATC. The RA then adjusted vertical speed to nearly level then gave us another climbing RA this time of about 1;500 fpm.  I again followed the TCAS RA; this time after following the guidance of the RA it cleared us of the conflict. The captain let ATC know both times about the TCAS RA and they were indifferent about what we had done.  We proceeded to follow the rest of the QUABN RNAV arrival with altitude and speeds on target.ATC should [have] never cleared VFR opposite direction traffic through an altitude that another aircraft was on.  ATC should [have] been more diligent in diverting the two airplanes away from each other.
The controller seemed unconcerned about the conflict. I thought it weird that they would have traffic climbing to an altitude above our bottom altitude but didn't have time to query the controller about the instruction given to the VFR aircraft.
EMB-145 flight crew reported they responded to an RA on descent into BOS when ATC apparently cleared a VFR aircraft through their altitude.