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MongoDB System Alert: Renaming a Collection Across Databases May Lead to Data Loss (SERVER-131805)

SERVER-131805

Written by Diogo

Issue Description

Date announced: October 15, 2026

Impact: In sharded clusters, renaming a collection to a different database (a cross-database rename) targeting a namespace that does not already exist can, if the operation is interrupted (for example, by a primary step-down) at one specific point, result in the complete and permanent loss of the source collection's data. The rename command reports success even when this occurs. This issue only affects unsharded source collections and does not apply to same-database renames or renames onto an already-existing destination.

MongoDB Versions Affected:

  • 5.0.0 - 5.0.34

  • 6.0.0 - 6.0.29

  • 7.0.0 - 7.0.43

  • 8.0.0 - 8.0.32

  • 8.3.0 - 8.3.11

Details

We have identified a critical issue affecting the rename collection operation in sharded clusters, which can result in complete loss of data in the collection being renamed. You may be impacted by this issue only if ALL the following are true:

  1. Your deployment is a sharded cluster.

  2. Your workload performs a rename collection operation where the source namespace and target namespace belong to different databases.

  3. The target collection does not exist prior to the rename operation.

  4. The source collection of the rename operation is unsharded.

The issue can then only occur on the small chance that the rename collection operation is interrupted midway (for example, a primary stepdown). The operation reports success even when this occurs. Your application receives no error, so you cannot detect this issue from the command's response alone.

The latest MongoDB patch versions (7.0.45+, 8.0.34+, 8.3.13+, 9.0.0+) already contain fixes for these issues.

Action Items

For MongoDB Atlas Customers: Atlas clusters have already been upgraded to versions containing a fix for this issue, unless you have configured a maintenance window. If you have a configured maintenance window, the change applies during the next scheduled window, or you may choose to apply the change immediately using the Begin Maintenance Now button.

If your application meets the criteria above, we recommend that you:

  • Avoid performing cross-database renames where the target namespace does not exist before upgrading.

  • Upgrade to the latest MongoDB patch version.

For more information, see SERVER-131805. If you have any questions, open a support case or start a chat with the Atlas Support team.

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