Overview
A significant security vulnerability, identified as CVE-2025-12970, has been discovered in the in_docker input plugin of Fluent Bit. This vulnerability stems from a buffer overflow in the extract_name function, potentially allowing attackers to cause a denial-of-service (DoS) or, in more severe scenarios, achieve arbitrary code execution.
Technical Details
The extract_name function within the in_docker input plugin is responsible for extracting container names. However, the function copies these names into a fixed-size stack buffer without proper length validation. An attacker who can influence container names (e.g., by creating containers or controlling existing container names) can exploit this by providing an excessively long container name. This overlong name overflows the buffer, potentially overwriting adjacent stack memory. The consequences can range from a simple process crash (DoS) to the execution of malicious code.
CVSS Analysis
While currently rated as N/A, it’s crucial to understand the potential severity of this vulnerability. A successful exploit could lead to a complete compromise of the Fluent Bit instance, and potentially, the underlying host system, depending on the privileges of the Fluent Bit process. A high CVSS score is anticipated upon a full vulnerability analysis.
Possible Impact
The impact of this vulnerability could be substantial, especially in environments where Fluent Bit is used to collect and forward logs from numerous containers. Potential consequences include:
- Denial of Service (DoS): An attacker could crash the Fluent Bit process, disrupting log collection and monitoring.
- Arbitrary Code Execution: In a more severe scenario, an attacker could leverage the buffer overflow to execute arbitrary code, potentially gaining control of the system running Fluent Bit.
- Data Breach: Compromised Fluent Bit instances could be used to intercept or manipulate sensitive log data.
Mitigation and Patch Steps
The vulnerability has been addressed in Fluent Bit version 4.1.0. It is strongly recommended that users upgrade to this version or a later version as soon as possible.
- Upgrade Fluent Bit: The most effective mitigation is to upgrade to Fluent Bit version 4.1.0 or later.
- Restrict Container Creation: If possible, limit who can create or rename containers in your environment.
- Monitor for Suspicious Activity: Monitor Fluent Bit logs for crashes or other unusual behavior.
