Elastic Cloud: Replication bug causing slow recoveries

Impact: majorStatus: resolvedStarted 2026-09-01 08:16 UTCResolved 2026-09-30 20:44 UTC (30 d)6 updatesSource: stspg.io

Summary

Elastic Cloud Hosted reported major degradation from 2026-09-01 08:16 UTC to 2026-09-30 20:44 UTC (29 days 12 h). In Elasticsearch 9.5.0, 9.5.1 and 9.5.2, bulk indexing could cause replica divergence, high disk usage and long-running recoveries. Elastic fixed the bug in 9.5.3 and advised affected customers to upgrade and follow workaround steps.

Machine-written from the archived incident (Sol). Check the timeline before relying on it.

Affected components: Elastic Cloud Hosted

Timeline of updates

investigating2026-09-01 08:16 UTC
We are aware of a bug affecting customers on Elasticsearch versions 9.5.0, 9.5.1 and 9.5.2 where bulk index operations processed on the primary shard can result in divergence on the replicas resulting in high disk usage and long-running recoveries. The team is working on a fix. More information can be found on https://www.elastic.co/docs/release-notes/elasticsearch/known-issues#elasticsearch-9.5.2-known-issues The next update will be in the next 2 hours or sooner if needed.
identified2026-09-01 11:07 UTC
We have identified the root cause and the team is working on a fix scheduled to be released in Elasticsearch version 9.5.3 What you can do: - If you have not yet upgraded to 9.5.*, you are not affected as upgrades to 9.5 have been disabled until 9.5.3 is released - If you are already running 9.5 and experience the symptoms of this issue, please contact Elastic Support. More information can be found on https://www.elastic.co/docs/release-notes/elasticsearch/known-issues#elasticsearch-9.5.2-known-issues
identified2026-09-01 15:46 UTC
The fix has been identified and backported to the Elasticsearch 9.5 patch branch. The teams are performing the needed validations before scheduling and rolling out the 9.5.3 release.
monitoring2026-09-03 12:13 UTC
Elasticsearch 9.5.3 has been released and all customers currently running 9.5.0, 9.5.1 or 9.5.2 are advised to update to this new version as soon as possible.
monitoring2026-09-03 15:47 UTC
Elasticsearch 9.5.3 has been released and all customers currently running 9.5.0, 9.5.1 or 9.5.2 are advised to update to this new version as soon as possible. Impacted customers are advised to follow the workaround steps from https://github.com/elastic/elasticsearch/issues/158212 after the upgrade.
resolved2026-09-30 20:44 UTC
This issue was resolved in the 9.5.3 release of Elasticsearch. Customers running versions 9.5.0, 9.5.1, or 9.5.2 of Elasticsearch are advised to update to a newer version as soon as possible.

Rewindex changes for this incident

Major incident: Replication bug causing slow recoveries 2026-09-01 08:16 UTC

Impact, status and times are the vendor’s own, as last archived. View on stspg.io (opens in new tab). Elastic Cloud profile · Recent Elastic Cloud incidents · Markdown · JSON