Apache Accumulo 2.1.6

17 Jul 2026

About

Apache Accumulo 2.1.6 is a patch release of the 2.1 LTM line. It contains bug fixes and minor enhancements. This version supersedes earlier 2.1 releases and users upgrading to 2.1 should upgrade directly to this version instead of any prior 2.1 release.

Important Security Fixes

  • #6478 - This version fixes a security flaw discovered in 2.1.4 and 2.1.5 that allowed an authenticated user without system permissions to issue a graceful shutdown request to all Accumulo services. This action could lead to a denial of service on an Accumulo cluster. While this action logged a message that the action was denied, the request would have been honored by the server, and the server would have still shut down.

Other Notable Changes

The following changes were made to improve performance and stability:

  • #6449 - The Garbage Collector was modified to use a server-side filter when processing candidate files to reduce memory usage.
  • #6470 - Some client code was updated to avoid some deadlocks that were possible if a user failed to close scanners before closing the AccumuloClient associated with them.
  • #6450, #6451 - Some data structures were changed throughout the code to set their expected size upon creation, in order to avoid resizing-related performance penalties.

Requirements

This version requires JDK 21 to build, but still supports Java 11 runtime.

Upgrading

View the Upgrading Accumulo documentation for guidance.

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