CVE-2025-67366
Published: 07 January 2026
Summary
CVE-2025-67366 is a high-severity Relative Path Traversal (CWE-23) vulnerability in Sylphx Filesystem-Mcp. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 23.5th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
This vulnerability is AI-related — categorised as AI Agent Protocols and Integrations; in the Protocol-Specific Risks risk domain.
The strongest mitigations our analysis identified are NIST 800-53 AC-3 (Access Enforcement) and SI-10 (Information Input Validation).
Deeper analysis
CVE-2025-67366 is a critical path traversal vulnerability (CWE-23) affecting version 0.5.8 of @sylphxltd/filesystem-mcp, an MCP server that provides file content reading functionality. The flaw exists in the "read_content" tool due to improper symlink handling in the path validation mechanism. Specifically, the resolvePath function performs path validity checks before resolving symlinks, while the underlying fs.readFile operation automatically resolves symlinks during file access. This discrepancy allows attackers to bypass directory restrictions. The vulnerability has a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).
Remote attackers require no privileges or user interaction to exploit this vulnerability over the network with low complexity. By placing symlinks within the allowed directory that point to files outside the intended operational scope, attackers can trick the read_content tool into accessing and disclosing unauthorized file contents. Successful exploitation results in high-impact confidentiality violations, enabling the reading of sensitive data beyond the server's restricted filesystem boundaries.
Further details, including potential patches or mitigation guidance, are documented in the project's GitHub repository at https://github.com/sylphxltd/filesystem-mcp and the associated issue tracker at https://github.com/sylphxltd/filesystem-mcp/issues/134. Security practitioners should review these resources for updates on remediation steps.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-1202
Vulnerability details
@sylphxltd/filesystem-mcp v0.5.8 is an MCP server that provides file content reading functionality. Version 0.5.8 of filesystem-mcp contains a critical path traversal vulnerability in its "read_content" tool. This vulnerability arises from improper symlink handling in the path validation mechanism: the resolvePath…
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function checks path validity before resolving symlinks, while fs.readFile resolves symlinks automatically during file access. This allows attackers to bypass directory restrictions by leveraging symlinks within the allowed directory that point to external files, enabling unauthorized access to files outside the intended operational scope.
- CWE(s)
AI Security AnalysisAI
- AI Category
- AI Agent Protocols and Integrations
- Risk Domain
- Protocol-Specific Risks
- OWASP Top 10 for LLMs 2025
- None mapped
- Classification Reason
- Matched keywords: mcp
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Remote unauthenticated path traversal in public-facing MCP file server directly enables T1190 exploitation and unauthorized local file reads (T1005).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
SI-10 mandates validation and sanitization of path inputs to prevent path traversal exploits arising from improper symlink handling in the resolvePath function.
AC-3 enforces approved access authorizations that directly counter unauthorized file reads outside the intended directory scope via symlink bypasses.
AC-6 applies least privilege to limit the filesystem-mcp server's read access, reducing the confidentiality impact of successful symlink-based path traversal.