CVE-2026-44160: Fluent Fluentd denial of service via decompression bomb in input plugins

CVE-2026-44160 · Severity: high · CVSS 7.5 · Published 2026-07-08

Fluentd is a popular data collection tool used to gather and route logs from various sources to storage systems. A vulnerability in how it handles compressed data allows an attacker to send a specially crafted "zip bomb" that expands to an enormous size when processed. This can exhaust the server's memory, causing the Fluentd service to crash and disrupting all log collection and data forwarding operations.

Technologies: fluentd (RubyGems). Vendors: RubyGems.

Quick answers

Is CVE-2026-44160 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-44160 being exploited in the wild.
How severe is CVE-2026-44160?
High severity, with a CVSS score of 7.5, published 8 July 2026.
Which products and versions are affected?
fluentd (RubyGems) <= 1.19.2, ECOSYSTEM:introduced=0,fixed=1.19.3.
Is there a fix for CVE-2026-44160?
Yes. fluentd (RubyGems): upgrade to 1.19.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-44160 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-44160?
Check whether you run fluentd (RubyGems) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • fluentd (RubyGems): upgrade to 1.19.3 or later
    bundle update fluentd

Technical details

A denial-of-service vulnerability exists in Fluentd's in_http and in_forward plugins due to improper handling of highly compressed data (CWE-409). While the software enforces limits on the size of incoming compressed payloads (via body_size_limit and chunk_size_limit), it fails to validate the size of the data after decompression. An unauthenticated remote attacker can exploit this by sending a 'gzip bomb'—a small compressed file that expands significantly in memory—leading to memory exhaustion and an Out-of-Memory (OOM) kill of the process. The issue is addressed in version 1.19.3 by introducing a decompression_size_limit and processing data in 64KB chunks.

Affected products

  • Fluent Fluentd < 1.19.3

Identifiers

  • CVE-2026-44160
  • GHSA-j9cw-hwqf-85w7

Timeline

  • 2026-06-25: patched: Fix merged and version 1.19.3 released.
  • 2026-06-26: advisory: GitHub Security Advisory GHSA-j9cw-hwqf-85w7 published.
  • 2026-07-08: disclosed: CVE-2026-44160 published to NVD.

References

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