# CVE-2026-44161 — fluent fluentd

> As of 2026-07-09, CVE-2026-44161 is a HIGH-severity vulnerability in fluent fluentd, CVSS v3.1 7.2, EPSS 0.4% (36.4th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-44161, most recently “Multiple Fluentd Vulnerabilities: RCE via Tag Placeholder (CVE-2026-44024), Info Disclosure (CVE-2026-44025), Decompression Bomb DoS (CVE-2026-44160), and SSRF (CVE-2026-44161)”.

**Last updated:** 2026-07-09

## What is CVE-2026-44161?

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.

The record classifies CVE-2026-44161 under weakness class [CWE-918](https://intel.threadlinqs.com/cwe/CWE-918). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 107 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 7.2 — HIGH (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:L`)
- **EPSS (FIRST):** 0.4% probability of exploitation in the next 30 days, higher than 36.4% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 5.1/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-07-08, last modified 2026-07-09

## Is CVE-2026-44161 being exploited?

It currently carries a trending score of 21 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [fluent](https://intel.threadlinqs.com/vendors/fluent): fluentd

Affected software packages:

- `rubygems:fluentd` — patched in 1.19.3

## How to fix CVE-2026-44161

The record marks a vendor fix as available for CVE-2026-44161. Fixed versions are recorded for 1 package: rubygems:fluentd 1.19.3. Patch reference: [https://github.com/fluent/fluentd/commit/c6a01ea2e0ea01977f8d615f7c6dbfae4cba88c9](https://github.com/fluent/fluentd/commit/c6a01ea2e0ea01977f8d615f7c6dbfae4cba88c9). Vendor advisory: [https://github.com/fluent/fluentd/security/advisories/GHSA-72f5-rr8c-r6gr](https://github.com/fluent/fluentd/security/advisories/GHSA-72f5-rr8c-r6gr). Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.

## Threat activity tracking CVE-2026-44161

1 tracked threat in the Threadlinqs corpus references CVE-2026-44161, either in the campaign’s CVE list or as an indicator on the campaign record.

- [Multiple Fluentd Vulnerabilities: RCE via Tag Placeholder (CVE-2026-44024), Info Disclosure (CVE-2026-44025), Decompression Bomb DoS (CVE-2026-44160), and SSRF (CVE-2026-44161)](https://intel.threadlinqs.com/threat/TL-2026-1041) — HIGH · 2026-07-01

## Sources

Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on 2026-10-10. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [github.com](https://github.com/fluent/fluentd/security/advisories/GHSA-72f5-rr8c-r6gr)

**Other references**

- [github.com](https://github.com/fluent/fluentd/pull/5394)
- [github.com (c6a01ea2e0ea01977f8d615f7c6dbfae4cba88c9)](https://github.com/fluent/fluentd/commit/c6a01ea2e0ea01977f8d615f7c6dbfae4cba88c9)
- [github.com (v1.19)](https://github.com/fluent/fluentd/releases/tag/v1.19.3)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-44161
Full detection coverage and IOCs for threats exploiting CVE-2026-44161 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp