Many lenders are not yet out with their first rate sheet of the day. Others tend to have a slightly higher bar for reprice risk when bonds sell off at this time of day. All that to say that reprice risk will vary quite a bit right now from "none at all" to "somewhat possible."

MBS are down exactly an eighth of a point from AM highs, and 2 ticks (.06) on the day.  10yr yields are still down just over half a bp on the day at 4.467.  

We're not seeing any obvious catalysts for the quick little sell-off, but it clearly began at 10:08am ET and resulted in only a modest increase in Treasury volume.