Five vulnerabilities have been identified in Fluent Bit. Upon a successful exploitation, attackers could bypass authentication, perform path traversal, execute remote code, or cause denial of service. Review this Cybersecurity Threat Advisory now to secure you or your clients’ infrastructure.
What is the threat?
Five Fluent Bit vulnerabilities have been identified that could be chained to compromised cloud and container environments:
- CVE-2025-12972: Path traversal flaw caused by unsanitized tag values that can overwrite files, tamper logs, or enable remote code execution.
- CVE-2025-12970: Stack buffer overflow in the Docker Metrics input plugin that could trigger code execution or crash the agent via long container names.
- CVE-2025-12978: Tag matching weakness that allows spoofing trusted tags, log rerouting, bypassing filters, and injecting malicious records under trusted tags.
- CVE-2025-12977: Improper input validation of user-controlled tag fields, enabling newline, traversal, and control-character injections that corrupt downstream logs.
- CVE-2025-12969: Missing authentication check in the in_forward plugin, enabling log submission, false telemetry, and fraudulent events in security logs. Together, these flaws enable data tampering, log manipulation, remote code execution, and disrupted telemetry across Fluent Bit deployments.
Why is it noteworthy?
Fluent Bit is a critical component for collecting and routing telemetry, making these flaws highly impactful. Exploitation could let attackers bypass authentication, manipulate logs, and seize control of data streams. A successful attack might enable stealthy lateral movement, expose sensitive information, and disrupt essential services.
What is the exposure or risk?
Fluent Bit deployments across cloud, container, and hybrid environments are at risk, especially where logs and telemetry feed centralized collectors or cloud services. An attacker typically needs network access to a Fluent Bit instance, a condition more likely when default settings are in place (e.g., no TLS, open ports for HTTP, Forward, TCP, or Syslog). Fluent Bit is ubiquitous—embedded in countless containers and cloud environments—so the potential attack surface is broad. The overall risk increases in systems with extensive logging and centralized dashboards, where attackers could move laterally or camouflage activities within log data.
An older flaw (Linguistic Lumberjack, CVE-2024-4323) also heightens the risk since it could enable denial-of-service DoS, information disclosure, or remote code execution, underscoring the need for timely patching and robust security controls.
What are the recommendations?
Barracuda recommends these actions to secure your cloud infrastructure:
- Apply patched Fluent Bit versions (4.0.12, 4.1.1, 4.2.0) to mitigate the flaws.
- Tighten access controls around Fluent Bit, enforce least-privilege, and use strong authentication.
- Harden logging pipelines by validating log integrity, enabling tamper-evident configurations, and monitoring for unusual data-forwarding patterns.
- Avoid using dynamic tags for routing; lock down output paths and destinations to prevent tag-based traversal, and run Fluent Bit with non-root privileges where feasible.
- Review container and cloud deployment practices, including image provenance and runtime security controls, and update incident response plans to address log tampering and data-enabled attacks.
References
For more in-depth information about the recommendations, please visit the following links:
- https://thehackernews.com/2025/11/new-fluent-bit-flaws-expose-cloud-to.html
- https://www.oligo.security/blog/critical-vulnerabilities-in-fluent-bit-expose-cloud-environments-to-remote-takeover
If you have any questions about this Cybersecurity Threat Advisory, don’t hesitate to get in touch with Barracuda Managed XDR’s Security Operations Center.
This post originally appeared on Smarter MSP.