MongoDB 4.2.7 Bug – Off-by-one overflow in block-modification bitmaps for incremental backup

A bug on MongoDB 4.2.7 has been identified- and a fix is included in 4.2.8 .Certain conditions are required for the bug to appear – detailed below. Based on the supporting documentation for the MongoDB 4.2.7  bug to occur:

  • Must be running MongoDB 4.2.7.
  • Managed by Ops Manager 4.2.13+ or managed in Cloud Manager with MongoDB agent version v10.14.0+.
  • Incremental backups are enabled.
  • The DB server has  collection files greater than 2GB on disk.
  • These collections are modified anytime after backups are enabled.

If these conditions are met , there is a possibility that MongoDB will improperly overwrite memory.

 

To fix you will need to upgrade the Replica Set version from 4.2.7 to 4.2.8 . The upgrade does require a host restart – so ensure all checks are made regarding data recovery points and any existing users connected

Author: Jack Vamvas

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