CVE-2021-36088 in Fluent Bit
Summary
by MITRE • 07/01/2021
Fluent Bit (aka fluent-bit) 1.7.0 through 1.7,4 has a double free in flb_free (called from flb_parser_json_do and flb_parser_do).
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Analysis
by VulDB Data Team • 07/04/2021
Fluent Bit is an open-source log data collection tool widely used for forwarding and processing log data in distributed systems environments. The vulnerability CVE-2021-36088 represents a critical double free memory corruption issue affecting versions 1.7.0 through 1.7.4 of this software. This flaw occurs within the memory management functions of the application where a pointer is freed twice, leading to potential arbitrary code execution or system instability. The vulnerability manifests in the flb_free function which is invoked from two distinct code paths: flb_parser_json_do and flb_parser_do, creating conditions where memory deallocation occurs more than once for the same memory block. Such double free conditions are particularly dangerous as they can be exploited by attackers to manipulate heap memory structures and potentially execute malicious code with the privileges of the running Fluent Bit process. The vulnerability aligns with CWE-415 which specifically addresses double free conditions in memory management operations, representing a fundamental flaw in resource handling that can lead to severe security implications. From an operational perspective, this vulnerability impacts organizations relying on Fluent Bit for log aggregation across containerized environments, microservices architectures, and cloud-native deployments where the software serves as a critical data collection component. Attackers exploiting this vulnerability could gain unauthorized access to log data, potentially leading to information disclosure, privilege escalation, or disruption of logging services that are essential for system monitoring and security operations. The ATT&CK framework categorizes this type of vulnerability under T1059.007 for command and script interpreter execution, as exploitation could enable attackers to execute arbitrary commands on affected systems. Organizations using Fluent Bit in production environments should prioritize immediate remediation by upgrading to version 1.7.5 or later, which contains the necessary memory management fixes. Additionally, implementing proper input validation and monitoring for abnormal memory allocation patterns can help detect potential exploitation attempts. The vulnerability underscores the importance of thorough memory management testing in logging and monitoring tools, particularly those operating in high-security environments where log integrity and system availability are paramount. System administrators should also consider implementing network segmentation and access controls around systems running Fluent Bit to limit potential attack surface and contain the impact of any successful exploitation attempts.