CVE-2025-67364 is a critical security vulnerability identified in fast-filesystem-mcp version 3.4.0, specifically within its file operation utilities including fast_read_file. The root cause is improper path validation logic that relies on path.resolve() to enforce directory access restrictions. However, path.resolve() does not resolve symbolic links to their actual physical paths, which allows attackers to craft symbolic links inside permitted directories that point to restricted or sensitive system paths. When these symlinks are accessed through otherwise valid path references, the validation functions safePath and isPathAllowed are bypassed, granting unauthorized file access. This path traversal flaw can lead to exposure or modification of sensitive files outside the intended directory scope, undermining confidentiality and integrity. The vulnerability does not require authentication or user interaction, increasing its exploitability. Although no public exploits are currently known, the vulnerability is classified as critical due to the potential for severe impact. The lack of a CVSS score necessitates an expert severity assessment. The vulnerability affects all deployments of fast-filesystem-mcp version 3.4.0, and no patches or mitigations have been officially released at the time of publication. Organizations relying on this software for file operations should urgently review their usage and implement additional symlink resolution checks or restrict symbolic link creation privileges until a patch is available.

The primary impact of CVE-2025-67364 is unauthorized access to sensitive files outside of intended directories, which can lead to data breaches, leakage of confidential information, or unauthorized modification of critical system files. For European organizations, especially those in sectors such as finance, healthcare, government, and critical infrastructure, this vulnerability could result in significant operational disruption and regulatory non-compliance under GDPR and other data protection laws. Attackers exploiting this flaw could gain access to system configuration files, credentials, or proprietary data, potentially enabling further lateral movement or privilege escalation. The vulnerability's ease of exploitation without authentication or user interaction increases the risk of automated or mass exploitation campaigns. The absence of known exploits in the wild currently limits immediate impact, but the critical nature of the flaw demands proactive mitigation to prevent future attacks. Organizations using fast-filesystem-mcp in cloud environments or shared hosting could face elevated risks due to multi-tenant exposure.

1. Immediately audit all instances of fast-filesystem-mcp version 3.4.0 in your environment and identify usage of vulnerable file operation tools such as fast_read_file. 2. Restrict or disable the creation and usage of symbolic links within directories accessible by these tools until a patch is available. 3. Implement additional path validation logic that fully resolves symbolic links to their physical paths before enforcing access controls, using secure libraries or custom code that handles symlink resolution correctly. 4. Employ file system monitoring to detect unusual symlink creation or access patterns indicative of exploitation attempts. 5. Limit permissions of processes running fast-filesystem-mcp tools to the minimum necessary, preventing access to sensitive directories even if symlink bypass occurs. 6. Engage with the software vendor or community to obtain patches or updates addressing this vulnerability as soon as they are released. 7. Consider deploying application-layer firewalls or endpoint detection solutions capable of identifying path traversal attempts. 8. Educate system administrators and developers about the risks of relying solely on path.resolve() for security checks and the importance of comprehensive symlink handling.