Please note that RT1900acemploys`wpa_supplicant' for EAPOL handshakes instead of`broadcom-sta' by default,but administrators are capable of force enabling the proprietary driver. Hence,Synology considers this vulnerability has limited impact on RT1900ac. For the"brcmfmac"concern,RT1900ac is not affected as it employs Broadcom proprietary driver instead of the open source version.  https://www.synology.com/products/RT1900ac
We are not aware of further vendor information regarding this vulnerability.