sys-fs/fuse-exfat-1.2.4 is in tree for > 30 days, been using it together with sys-fs/exfat-utils-1.2.4 without problems on 2 of my boxes. Last stable 1.0.1 is from 2013. Since then many bugs got fixed: https://github.com/relan/exfat/blob/master/ChangeLog
*** This bug has been marked as a duplicate of bug 589602 ***