Several high-severity flaws in the widely used Fluentd log collector could lead to remote code execution (RCE), data leaks, and denial-of-service attacks across multiple components.
The most critical issue, tracked as GHSA-44hj-4m45-frj3, has now been assigned CVE-2026-44024 and allows remote code execution through improper handling of the ${tag} placeholder.
This vulnerability enables attackers to perform arbitrary file writes on the host system. By exploiting this behavior, an attacker can overwrite configuration files or inject malicious code, eventually gaining full control over the affected system.
The issue becomes more dangerous in environments where Fluentd processes untrusted log data, as attackers can craft malicious input to trigger the vulnerability remotely.
Security researchers note that this flaw directly affects systems that use dynamic placeholder expansion without proper validation.
Another high-severity vulnerability, GHSA-pr7j-96cj-549h, corresponds to CVE-2026-44025 and affects the Monitor Agent API. This flaw can expose sensitive information, including system metrics and configuration details.
Attackers can use this information to understand the target environment better and plan subsequent attacks.
Multiple Fluentd Vulnerabilities
Fluentd is also vulnerable to a denial-of-service condition tracked as GHSA-j9cw-hwqf-85w7, mapped to CVE-2026-44160. This issue is caused by improper handling of gzip-compressed data in the in_http and in_forward plugins.
Attackers can exploit this by sending specially crafted gzip payloads, known as decompression bombs, which consume excessive memory and crash the service.
In addition, a server-side request forgery vulnerability, identified as GHSA-72f5-rr8c-r6gr and assigned CVE-2026-44161, impacts the out_http plugin. This flaw allows attackers to manipulate outgoing HTTP requests through unsafe placeholder expansion.
As a result, attackers may access internal services or sensitive cloud metadata endpoints, potentially leading to credential exposure.
According to GitHub Security Advisories, older vulnerabilities, including insecure deserialization (CVE-2022-39379) and a regular expression denial-of-service flaw (CVE-2021-41186), remain relevant in some configurations and can increase overall risk when combined with newly disclosed issues.
Fluentd is commonly deployed in centralized logging systems, including cloud and Kubernetes environments, making it an attractive target for attackers. A successful exploit can provide access to critical infrastructure and enable lateral movement across networks.
For example, an attacker could send a specially crafted log entry containing a manipulated ${tag} value. This could force Fluentd to write malicious files to the system, ultimately leading to remote command execution.
Organizations using Fluentd are advised to update to the latest patched versions and review their configurations carefully.
Securing APIs, limiting exposure to untrusted inputs, and monitoring abnormal activity are essential steps to reduce the risk of exploitation.
