v4.2.5

KNOWLEDGE BASE

Release Notes v4.2.5

Fluent Bit is a Fast and Lightweight Data Processor and Forwarder for Linux, BSD, Windows and macOS. We are proud to announce the availability of Fluent Bit v4.2.5.

Below is a detailed list of changes included in this release…

What’s new ?

Fluent Bit v4.2.5 is a broad maintenance release hardening the core engine, compression handling, protocol parsers, and multiple input and output plugins. It adds Ubuntu 26.04 packaging support and a bash-style default value operator for environment variable expansion. For security-sensitive areas, several out-of-bounds read and integer overflow issues in input protocol handlers are resolved.

Core

• env: add bash-style default value operator :- for environment variable expansion
• input_thread: replace raw read() with pipe abstraction to fix a crash on thread exit
• network: handle bracketed IPv6 address literals correctly
• parser: fix incorrect timezone assignments on timestamps at midnight
• routing: fix missing input alias causing pipeline routing failures
• engine: ignore duplicate STOP signals to prevent shutdown spin loops
• utils: fix integer divide-by-zero on Windows x64 in bytes_to_human_readable_size
• mp: fix record count when processing empty data
• avro: handle 64-bit integer values correctly
• zstd: cap decompression buffer at maximum size instead of aborting on overshoot
• snappy: read Snappy frame length as 3 bytes to avoid out-of-bounds read at boundary
• aws: compression: set correct block size for Arrow compression
• crypto: fix build when OPENSSL_NO_ENGINE is defined
• packaging: add support for Ubuntu 26.04 (Noble successor)

Libraries

• No bundled library upgrades in this release.

Plugins

• Tail (Input)
  • fix file append state cleanup on append failure
• Collectd (Input)
  • reject protocol parts with length less than 4 and fix null-terminator out-of-bounds write
• Forward (Input)
  • handle unpacker allocation failure gracefully
  • validate array size before accessing message-mode record fields
• Syslog (Input)
  • fix integer overflow in octet-counting frame length parser
• MQTT (Input)
  • fix out-of-bounds read caused by hardcoded remaining-length overhead
• Elasticsearch (Input)
  • check map size before accessing the first entry in bulk request validation
• Dummy (Input)
  • use pre_run callback to fix crash on plugin initialization failure
• Kubernetes (Filter)
  • avoid recycling connections in fetch_pod_service_map to prevent stale connection use
  • destroy TLS session to prevent SSL object leak
  • destroy upstream and TLS context on normal exit path
• Chronicle (Output)
  • add label and namespace mapping support for native out-of-band metadata
• InfluxDB (Output)
  • fix tag key handling failure in output formatting
• LogDNA (Output)
  • remove promoted known keys that caused incorrect field handling
• Azure Logs Ingestion (Output)
  • fix segmentation fault on plugin termination

Join us

We want to hear about you, our community is growing, and you can be part of it!, you can contact us at:

• Github: http://github.com/fluent/fluent-bit
• Slack: http://slack.fluentd.org
• Twitter: @fluentbit