CVE-2026-44025 in Fluentd
Summary
by MITRE • 07/09/2026
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's Monitor Agent plugin in_monitor_agent exposes internal metrics and plugin information via a REST API, and responses from /api/plugins.json and related endpoints unintentionally include internal instance variables that may contain database passwords, API keys, or cloud credentials. This issue is fixed in version 1.19.3.
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Analysis
by VulDB Data Team • 07/09/2026
The vulnerability in Fluentd's Monitor Agent plugin represents a critical information disclosure flaw that directly impacts the security posture of systems relying on this logging and data collection framework. Prior to version 1.19.3, the in_monitor_agent plugin provides a REST API interface for monitoring internal system metrics and plugin configurations, which is designed for operational purposes but inadvertently exposes sensitive internal state information through its response endpoints. This flaw falls under the category of CWE-200 - Information Exposure, where system internals are disclosed to unauthorized parties through improper access control or data handling mechanisms.
The technical implementation of this vulnerability stems from the plugin's REST API responses containing unfiltered internal instance variables that may include database credentials, API keys, and cloud service authentication tokens. When attackers make requests to endpoints such as /api/plugins.json and related monitoring interfaces, they receive structured responses that include not only legitimate monitoring data but also sensitive configuration parameters that should remain confidential. This occurs because the plugin's response generation logic does not properly sanitize or filter internal variables before including them in API responses, creating an information leak that directly violates the principle of least privilege and data confidentiality.
The operational impact of this vulnerability extends beyond simple credential exposure, as it provides attackers with comprehensive insights into the internal architecture and configuration of Fluentd instances. An attacker who gains access to these monitoring endpoints can extract database connection strings containing passwords, API keys for cloud services, and other authentication tokens that could be used to compromise additional systems within the network. This information disclosure creates a significant attack surface that could enable lateral movement, data exfiltration, and privilege escalation attacks against connected databases, cloud services, and other infrastructure components that rely on the exposed credentials.
Organizations using Fluentd versions prior to 1.19.3 face substantial risk from this vulnerability, as it essentially provides attackers with a backdoor into their monitoring infrastructure that could be exploited to gain access to critical system credentials. The exposure of database passwords through the REST API endpoints creates immediate opportunities for attackers to directly connect to backend databases and extract or modify sensitive information. Additionally, cloud service credentials exposed through this vulnerability could enable attackers to access cloud storage, compute resources, or other services that are integral to the organization's infrastructure.
The mitigation strategy involves upgrading to Fluentd version 1.19.3 or later, which implements proper filtering of internal instance variables in API responses to prevent credential exposure. Organizations should also implement network segmentation and access controls to limit exposure of monitoring endpoints to authorized personnel only, while conducting regular audits of monitoring configurations to ensure sensitive data is not inadvertently exposed through other interfaces. This vulnerability demonstrates the importance of secure coding practices and input/output sanitization in monitoring systems, particularly those that provide administrative interfaces for system diagnostics and configuration inspection, aligning with ATT&CK technique T1567 - Exfiltration Over Web Service which covers methods of data extraction through web service APIs.
The remediation process should include comprehensive testing to ensure that all monitoring endpoints properly filter sensitive information while maintaining functionality for legitimate operational use cases. Security teams should also implement logging and monitoring of access to these endpoints to detect unauthorized access attempts and establish baseline behavior for normal operational activity, which can help identify potential exploitation attempts in the future.