Full Report
Cybersecurity researchers have discovered five vulnerabilities in Fluent Bit, an open-source and lightweight telemetry agent, that could be chained to compromise and take over cloud infrastructures. The security defects "allow attackers to bypass authentication, perform path traversal, achieve remote code execution, cause denial-of-service conditions, and manipulate tags," Oligo Security said in
Analysis Summary
This summary focuses on the five newly disclosed vulnerabilities in Fluent Bit as detailed in the context provided. Note that specific severity scores (CVSS) for each individual CVE were not explicitly mentioned in the source text, so they are marked as "N/A" in the summary.
# Vulnerability: Chained Flaws in Fluent Bit Leading to Cloud Takeover
## CVE Details
| CVE ID | CVSS Score | Severity | CWE (Implied) |
| :--- | :--- | :--- | :--- |
| CVE-2025-12972 | N/A | N/A | Path Traversal (CWE-22) |
| CVE-2025-12970 | N/A | N/A | Buffer Overflow (CWE-121) |
| CVE-2025-12978 | N/A | N/A | Authentication Bypass/Improper Access Control |
| CVE-2025-12977 | N/A | N/A | Improper Input Validation |
| CVE-2025-12969 | N/A | N/A | Missing Authentication |
## Affected Systems
- **Products:** Fluent Bit (open-source telemetry agent)
- **Versions:** Versions prior to 4.1.1 and 4.0.12 are presumed vulnerable.
- **Configurations:** Any deployment using the affected input plugins or configurations that rely on user-controlled tag values for output file generation.
## Vulnerability Description
Five distinct vulnerabilities exist in Fluent Bit that can be chained to compromise cloud infrastructures. The flaws include:
1. **CVE-2025-12972 (Path Traversal):** Unsanitized tag values are used to generate output filenames, allowing an attacker to write or overwrite arbitrary files on disk, potentially leading to Remote Code Execution (RCE).
2. **CVE-2025-12970 (Stack Buffer Overflow):** Occurs in the `in_docker` input plugin when containers have excessively long names, which can result in code execution or agent crash (DoS).
3. **CVE-2025-12978 (Tag Spoofing):** Flaw in tag-matching logic allows attackers to guess the first character of a `Tag_Key` to spoof trusted tags, enabling log rerouting and injection of misleading records.
4. **CVE-2025-12977 (Input Validation):** Improper validation of tags derived from user-controlled fields allows injection of newlines, traversal sequences, and control characters, corrupting downstream logs.
5. **CVE-2025-12969 (Missing Authentication):** Missing `security.users` authentication in the `in_forward` plugin allows unauthenticated external Fluent Bit instances to send logs, inject false telemetry, or flood services.
## Exploitation
- **Status:** Research conducted by Oligo Security; exploitation scenario discussed is targeted, indicating potential for hostile use or proof-of-concept development.
- **Complexity:** Likely Medium, as chaining multiple flaws (e.g., tag manipulation leading to path traversal RCE) is described.
- **Attack Vector:** Remote (via manipulated logs/inputs) and Network.
## Impact
- **Confidentiality:** High (Ability to hide tracks by erasing or rewriting incriminating entries; manipulating log data).
- **Integrity:** Critical (RCE: execute malicious code; Log tampering; Injecting fake telemetry).
- **Availability:** Medium/High (DoS conditions possible via buffer overflow or log flooding).
## Remediation
### Patches
- Fluent Bit **versions 4.1.1** and **4.0.12** (released the previous month) address these issues. **Immediate upgrade is required.**
### Workarounds
- Avoid using dynamic tags for routing decisions.
- Lock down output paths and destinations to prevent tag-based path expansion/traversal.
- Mount `/fluent-bit/etc/` and configuration files as read-only to block runtime tampering.
- Run the Fluent Bit service as non-root users.
## Detection
- **Indicators of Compromise:** Unprecedented file write activity originating from the Fluent Bit process, unexpected log data under supposedly trusted tags, log data corruption, or unexpected restarts/crashes of the Fluent Bit service.
- **Detection Methods and Tools:** Monitor outbound file write operations originating from the Fluent Bit process that target sensitive system areas. Monitor for unusual traffic to the `in_forward` endpoint if external logging is enabled without proper authentication.
## References
- Oligo Security Report: hxxps://www.oligo.security/blog/critical-vulnerabilities-in-fluent-bit-expose-cloud-environments-to-remote-takeover
- Fluent Bit Release Notes (Implied): Check GitHub documentation for versions 4.1.1 and 4.0.12.