Apache Kafka Release Notes

Highlights from current and recent Apache Kafka releases. For complete, patch-level detail, see the upstream release notes linked at the bottom of each version stream.

4.3.x

Kafka 4.3.1 - Current Release

Patch release for the 4.3 line, focused on memory-leak and group-coordinator fixes. The release notes do not state a release date.

RocksDB memory leaks fixed (KAFKA-20616, KAFKA-20688) — Close-path leaks in RocksDBStore and a leak in RocksDBTimestampedStoreWithHeaders that caused native memory growth and eventual out-of-memory errors
Group coordinator errors after leadership changes (KAFKA-20634, KAFKA-20635) — Spurious errors following partition leadership changes are no longer raised
Consumer group migration policy (KAFKA-20640) — Classic members are no longer accepted when the migration policy is disabled
AdminClient partition-leader hang (KAFKA-20673) — Partition-leader API calls no longer hang when a cached leader has left the cluster
Stale changelog offsets (KAFKA-20663) — Stale persisted changelog offsets that caused OffsetOutOfRangeException on restart are corrected
Clean downgrade from 4.3 (KAFKA-20543) — The RocksDB offsets column family is dropped on clean shutdown when downgrading from 4.3

Kafka 4.3.0 (May 2026) - Major Release

OAuth2 private_key_jwt client assertion (KAFKA-18608) — Support for the private_key_jwt client authentication method in the OAuth2 client, removing the need to embed client secrets in configuration
Topic auto-creation honors controller defaults (KAFKA-19655) — num.partitions and default.replication.factor from controller properties are applied consistently when topics are auto-created
Broker and log-directory cordoning (KAFKA-19774) — Mechanism to cordon brokers and individual log directories, preventing new partition placement while preserving existing replicas (useful for staged decommissioning and maintenance)
Share Groups configuration enhancements (KAFKA-20037) — Additional group-level configurations for share groups, including dynamic group-level overrides
Assignment epochs for consumer groups (KIP-1251, KAFKA-20066) — Epoch tracking on group assignments to detect and reconcile stale state during rebalances
Header-aware state stores in Kafka Streams (KAFKA-20056, KAFKA-20194) — Record headers can be stored in state stores; DSL opt-in support for header-aware KeyValue, Window, and Session stores
State-store managed changelog offsets — Changelog offsets managed within the state store, reducing reliance on external offset tracking
Group coordinator executor — Configurable threading model and metrics for the group coordinator with assignment batching and offload at broker and group levels
Tiered storage improvements — Snapshot fetches behave correctly on slow networks; broader stability work in the tiered-storage path
KeyValueStore approximateNumEntries metric — Approximate entry count exposed as a metric for operational visibility

Deprecations (marked for removal in a future release):

Broker-level group.coordinator.rebalance.protocols config (KAFKA-19740)
streams-scala module (KAFKA-19976)

Security fixes:

CVE-2025-5115 (Jetty upgrade)
CVE-2025-67030 (plexus-utils)
GHSA-72hv-8253-57qq (Jackson core)
CVE-2026-28390, CVE-2026-22184 (native image libraries)

For full 4.3.x release notes, see the Apache Kafka downloads page.

4.2.x

Kafka 4.2.0 (February 2026)

Share Groups enhancements (KIP-932) — RENEW acknowledgement type for extending processing timeouts (KIP-1222), configurable ShareAcquireMode with batch_optimized and record_limit modes (KIP-1206), share partition lag metrics (KIP-1226)
Streams Rebalance Protocol GA (KIP-1071) — Server-side rebalance protocol with broker-coordinated task assignment, promoted from early access to generally available
Kafka Streams dead letter queue (KIP-1034) — Dead letter queue support in Streams exception handlers
Kafka Streams CloseOptions API (KIP-1153) — Fluent-style API with explicit leave-group control
Anchored punctuation (KIP-1146) — Optional startTime parameter for wall-clock punctuation scheduling
Standardized CLI arguments (KIP-1147) — Consistent --bootstrap-server and --command-config across all tools; legacy argument variants deprecated
External schema in JsonConverter (KIP-1054) — schema.content configuration for external schemas, reducing message sizes
Allowlist connector override policy (KIP-1188) — New connector client configuration override policy based on allowlists
Controller idle metrics (KIP-1190, KIP-1229) — AvgIdleRatio metric for controller thread and MetadataLoader idleness
Metric naming correction (KIP-1100) — Metric names corrected to follow kafka.COMPONENT convention
Adaptive coordinator batching (KIP-1224) — Automatic linger time adjustment for group and share coordinators
Thread-safe RecordHeader (KIP-1205) — Thread-safety improvements using double-checked locking
KafkaPrincipalBuilder enforcement (KIP-1157) — KafkaPrincipalBuilder now extends KafkaPrincipalSerde for compile-time enforcement
Rack ID in Admin API (KIP-1227) — Rack ID exposure in MemberDescription and ShareMemberDescription
KRaft auto-join (KIP-1186) — AckWhenCommitted flag in AddRaftVoterRequest for auto-join support

Deprecations (marked for removal in Kafka 5.0):

ConsumerGroupMetadata constructors (KIP-1136)
MX4j support (KIP-1193)
BrokerNotFoundException (KIP-1195)
Misspelled PARTITIONER_ADPATIVE_PARTITIONING_ENABLE constant (KIP-1175); use corrected spelling

4.1.x

Kafka 4.1.1 (November 2025)

Bug fixes and stability improvements

Kafka 4.1.0 (September 2025)

Queues for Kafka preview (KIP-932) - Promoted from early access to preview (4.0 early-access clusters cannot upgrade directly)
Streams Rebalance Protocol (KIP-1071) - Early access broker-coordinated rebalancing for Kafka Streams
OAuth jwt-bearer grant (KIP-1139) - New grant type avoiding secrets in configuration
Plugin metrics (KIP-877) - Plugins and connectors can register metrics via Monitorable interface
Connector versioning - Install and run multiple versions of same connector plugins
Transaction filtering (KIP-1152) - Transactional ID pattern filter in ListTransactions API
Consumer close options - New Consumer.close(CloseOptions) method controlling group leave behavior
Rack-aware assignment - Memory efficiency improvements for large consumer groups
KRaft voter upgrade (KIP-853) - Upgrade voters from static to dynamic configuration
High-watermark fix (KIP-1166) - Fixes pending fetch requests blocking high-watermark progression

4.0.x

Kafka 4.0.1 (October 2025)

Fixes 49 issues since 4.0.0 release

Kafka 4.0.0 (March 2025) - Major Release

ZooKeeper removed - KRaft is now the only metadata management mode
New Consumer Group Protocol GA (KIP-848) - Dramatically faster rebalances
Queues for Kafka early access (KIP-932) - Traditional queue semantics (promoted to preview in 4.1)
Java 17 required for brokers, Connect, and tools (Java 11 for clients)
Log4j2 replaces Log4j 1.x
MirrorMaker 1 removed - Use MirrorMaker 2

3.9.x

Kafka 3.9.1 (May 2025)

Fixes 66 issues since 3.9.0 release

Kafka 3.9.0 (November 2024)

Dynamic KRaft quorum (KIP-853) - Add/remove controllers without downtime
Final 3.x release before ZooKeeper removal

3.8.x

Kafka 3.8.1 (October 2024)

Fixes 17 issues since 3.8.0 release

Kafka 3.8.0 (July 2024)

Compression level configuration (KIP-390)
Tiered storage JBOD compatibility (early access)

3.7.x

Kafka 3.7.2 (December 2024)

Fixes 22 issues since 3.7.1 release

Kafka 3.7.1 (June 2024)

Bug fixes and stability improvements

Kafka 3.7.0 (February 2024)

JBOD in KRaft (KIP-858) - Early access
Client metrics (KIP-714)
Next-gen consumer rebalance (KIP-848) - Early access

Apache Kafka Downloads - Per-version release notes and binaries
Kafka Improvement Proposals (KIPs)
Version Compatibility and KRaft Migration Timeline