A new report out today from Oligo Cyber Security Ltd. details a new chain of five critical vulnerabilities in the widely deployed open-source logging agent Fluent Bit that exposes cloud environments to remote takeover.

Fluent Bit is an open-source agent that’s used to collect, process and forward logs, metrics and traces across cloud and containerized environments that sits on the ingestion path in systems such as Kubernetes, reads from local sources and then sends data to backends such as cloud services, databases, or security information and event management platforms. It’s used more than 15 billion times and embedded across cloud platforms, Kubernetes clusters and enterprise applications.

It’s at the center of observability pipelines for artificial intelligence labs, banks, software-as-a-service providers and major infrastructure operators. Because it sits directly on ingestion paths and handles untrusted data from containers, files and network endpoints, the vulnerabilities create serious pathways for attackers to manipulate logs, inject code and compromise cloud workloads.

The vulnerabilities in Fluent Bit allow attackers to bypass authentication, perform path traversal, overwrite files, hijack routing logic and trigger stack buffer overflows.

The most severe vulnerability, CVE-2025-12972, was found to occur from unsanitized tags being used to generate output filenames. Exploiting the vulnerability, an attacker could use “../” sequences to write or overwrite arbitrary files on disk to gain full remote code execution.

Other vulnerabilities allow attackers to forge tags by guessing a single character, manipulate routing, inject newlines and escape sequences into downstream logs, or create long Docker container names to trigger a stack buffer overflow that can crash the agent or execute arbitrary code.

Some of the affected code paths are said to have been present for more than eight years. The vulnerabilities were disclosed by Oligo in collaboration with Amazon Web Services Inc. through a coordinated vulnerability disclosure process.

The good news is that AWS has already secured its internal systems and released Fluent Bit version 4.1.1, and it’s urging customers to upgrade immediately.

AWS is also recommending that users use Amazon Inspector, AWS Security Hub and AWS Systems Manager to help assess exposure and remediate vulnerable workloads.

The report concludes by highlighting challenges in open-source security. Oligo says the coordinated disclosure required the involvement of a major cloud provider before the vulnerabilities could be acted upon.

“Despite multiple responsible disclosure attempts through official channels, it took more a week and the involvement of a major cloud provider before the vulnerabilities received sustained attention and remediation,” Oligo noted in its research. The process of assigning CVEs also took several weeks.

“The takeaway is clear: The security reporting and CVE assignment process for critical open-source infrastructure is still fragmented and fragile and collaboration between maintainers, cloud providers and security researchers is essential to keep the global software supply chain secure,” the report added.

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