BIT-fluentd-2026-44161: Fluentd: Server-Side Request Forgery (SSRF) via Placeholder Expansion in `out_http`
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.
AI Analysis
Technical Summary
The out_http plugin in Fluentd is vulnerable to SSRF due to placeholder expansion in the HTTP endpoint configuration. An attacker can exploit this by controlling placeholder values derived from untrusted input, causing Fluentd to send HTTP requests to arbitrary internal or external hosts. This can lead to unauthorized access to internal APIs or cloud metadata services. The vulnerability is identified as CWE-918 and affects all Fluentd versions before 1.19.3. The issue is addressed by an official patch in version 1.19.3.
Potential Impact
An unauthenticated attacker can exploit this vulnerability to make Fluentd send HTTP requests to arbitrary destinations, including internal network services or cloud metadata endpoints. This can result in unauthorized information disclosure (confidentiality impact) and partial denial of service (availability impact). Integrity impact is not indicated. The vulnerability has a high severity rating.
Mitigation Recommendations
An official patch is available in Fluentd version 1.19.3. Users should upgrade to this version to remediate the vulnerability. Until patched, mitigations include avoiding the use of dynamic hostnames in HTTP endpoint configurations, restricting network access to sensitive internal IP addresses, and filtering allowed hosts in placeholder expansions to prevent untrusted input from controlling request destinations.
BIT-fluentd-2026-44161: Fluentd: Server-Side Request Forgery (SSRF) via Placeholder Expansion in `out_http`
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.
CVSS v3.1
Score 7.2high
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The out_http plugin in Fluentd is vulnerable to SSRF due to placeholder expansion in the HTTP endpoint configuration. An attacker can exploit this by controlling placeholder values derived from untrusted input, causing Fluentd to send HTTP requests to arbitrary internal or external hosts. This can lead to unauthorized access to internal APIs or cloud metadata services. The vulnerability is identified as CWE-918 and affects all Fluentd versions before 1.19.3. The issue is addressed by an official patch in version 1.19.3.
Potential Impact
An unauthenticated attacker can exploit this vulnerability to make Fluentd send HTTP requests to arbitrary destinations, including internal network services or cloud metadata endpoints. This can result in unauthorized information disclosure (confidentiality impact) and partial denial of service (availability impact). Integrity impact is not indicated. The vulnerability has a high severity rating.
Mitigation Recommendations
An official patch is available in Fluentd version 1.19.3. Users should upgrade to this version to remediate the vulnerability. Until patched, mitigations include avoiding the use of dynamic hostnames in HTTP endpoint configurations, restricting network access to sensitive internal IP addresses, and filtering allowed hosts in placeholder expansions to prevent untrusted input from controlling request destinations.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-72f5-rr8c-r6gr
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-44161"]
- Ecosystems
- ["RubyGems"]
- Database Specific Severity
- HIGH
- Cvss Version
- 3.1
Threat ID: 6a3ef79627e9c79719ff8e74
Added to database: 06/26/2026, 22:05:10 UTC
Last enriched: 07/09/2026, 08:11:11 UTC
Last updated: 08/10/2026, 00:41:16 UTC
Views: 93
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