Segment fault crash on primary

Twice in the last 12 hours our primary server has encountered segment faults and crashed. Both times the stack trace appears to be the same. The server restarts without any problems reported in the log.

The primary server is a single shard with a single secondary and arbiter. We are running 2.6.5 on all servers. Mongos servers run on all application servers. We upgraded from 2.4.9 a week ago and ran without any problems until we encountered this crash. DB is small to moderate size (455GB) and recently rebuilt.