CVE-2025-12977

Comprehensive Technical Analysis of CVE-2025-12977

1. Vulnerability Assessment and Severity Evaluation

CVE ID: CVE-2025-12977 CVSS Score: 9.1

The vulnerability in Fluent Bit's in_http, in_splunk, and in_elasticsearch input plugins is critical due to the failure to sanitize tag_key inputs. This allows attackers to inject special characters such as newlines or path traversal sequences (../), which can be exploited to manipulate log routing, filenames, and contents. The high CVSS score of 9.1 indicates a severe vulnerability that can significantly impact data integrity and log routing.

2. Potential Attack Vectors and Exploitation Methods

• Newline Injection: Attackers can inject newlines into tag_key values, leading to log misrouting and potential forged record injection.
• Path Traversal: By injecting ../ sequences, attackers can manipulate file paths, potentially accessing or overwriting files outside the intended directory.
• Forged Record Injection: Attackers can inject malicious records into logs, affecting the integrity of log data.
• Log Misrouting: Manipulating tag_key values can reroute logs to unintended destinations, disrupting log analysis and monitoring.

3. Affected Systems and Software Versions

The vulnerability affects Fluent Bit versions prior to v4.1.0. Systems using these versions with the in_http, in_splunk, and in_elasticsearch input plugins are at risk. Organizations relying on Fluent Bit for log management and processing should prioritize updating to the latest version.

4. Recommended Mitigation Strategies

• Update to the Latest Version: Upgrade Fluent Bit to version v4.1.0 or later, which includes fixes for this vulnerability.
• Input Validation: Implement additional input validation and sanitization mechanisms to ensure that tag_key values do not contain special characters.
• Network Segmentation: Limit network access to Fluent Bit instances to trusted sources only.
• Monitoring and Logging: Enhance monitoring and logging to detect and respond to any suspicious activities related to log routing and file manipulation.
• Regular Audits: Conduct regular security audits and vulnerability assessments to identify and mitigate similar issues proactively.

5. Impact on Cybersecurity Landscape

The vulnerability highlights the importance of input validation and sanitization in log management systems. Organizations must ensure that all inputs are properly sanitized to prevent injection attacks and path traversal. The high CVSS score underscores the potential for significant disruption in log management and data integrity, emphasizing the need for robust security practices in log processing pipelines.

6. Technical Details for Security Professionals

• Vulnerability Type: Input Validation Error
• Affected Components: in_http, in_splunk, in_elasticsearch input plugins
• Exploitation: Attackers can inject special characters into tag_key values, leading to newline injection, path traversal, forged record injection, and log misrouting.
• Mitigation: Upgrade to Fluent Bit v4.1.0 or later, implement additional input validation, and restrict network access.
• Detection: Monitor for unusual log routing patterns, unexpected file modifications, and anomalous log entries.

Conclusion

CVE-2025-12977 represents a critical vulnerability in Fluent Bit that can be exploited to compromise log management and data integrity. Organizations must prioritize updating to the latest version of Fluent Bit and implement robust input validation and monitoring practices to mitigate the risk. This vulnerability serves as a reminder of the importance of thorough input sanitization in maintaining secure and reliable log processing systems.