CVE-2025-12972 is a path traversal vulnerability identified in the Fluent Bit logging tool, specifically within its out_file plugin. Fluent Bit is widely used for log collection and forwarding in cloud-native and containerized environments. The vulnerability arises because the out_file plugin does not properly sanitize tag values when deriving output file names if the File option is omitted. Tags are user-controllable metadata used to route logs, and an attacker with network access can craft tags containing path traversal sequences (e.g., '../') to manipulate the file path. This manipulation allows the attacker to cause Fluent Bit to write files outside the intended output directory, potentially overwriting critical files or placing malicious files in unauthorized locations. The CVSS 3.1 score is 5.3 (medium severity), reflecting that the attack vector is network-based with low complexity and no privileges or user interaction required. The impact is limited to integrity, as confidentiality and availability are not affected. No known exploits have been reported yet, but the vulnerability poses a risk in environments where Fluent Bit is exposed to untrusted network inputs. The lack of a patch link suggests that a fix may not yet be available, emphasizing the need for immediate mitigation steps.

For European organizations, this vulnerability could lead to unauthorized file writes on systems running Fluent Bit, potentially allowing attackers to alter log files, inject malicious content, or disrupt log integrity. This undermines trust in logging data, which is critical for incident response and compliance with regulations such as GDPR. While it does not directly compromise confidentiality or availability, the integrity impact can facilitate further attacks or cover tracks of malicious activity. Organizations relying heavily on Fluent Bit for centralized logging, especially in cloud, container, or microservices environments, are at higher risk. The vulnerability could also affect managed service providers and cloud platforms operating in Europe that use Fluent Bit internally or offer it as part of their logging solutions. The risk is heightened in environments where Fluent Bit instances are exposed to untrusted networks or receive logs from external sources without strict validation.

1. Immediately review Fluent Bit configurations to ensure the File option is explicitly set in the out_file plugin to prevent reliance on tag-derived file names. 2. Implement strict input validation and sanitization for all tag values before they reach Fluent Bit, filtering out path traversal sequences and other malicious characters. 3. Restrict network access to Fluent Bit instances, limiting log input sources to trusted and authenticated systems only. 4. Monitor file system changes in directories used by Fluent Bit for unexpected file creations or modifications. 5. Employ application-level sandboxing or containerization to limit the impact of unauthorized file writes. 6. Stay updated with Fluent Bit vendor advisories for patches or official fixes and apply them promptly once available. 7. Consider deploying Web Application Firewalls (WAFs) or Intrusion Detection Systems (IDS) with rules targeting path traversal attempts in log tags. 8. Conduct regular security audits and penetration tests focusing on log ingestion pipelines to detect similar vulnerabilities.