CVE-2025-53110: MCP Filesystem Path Traversal Vulnerability

CVE-2025-53110 Overview

CVE-2025-53110 is a Path Traversal vulnerability affecting the Model Context Protocol (MCP) Servers, specifically the Filesystem component. This vulnerability allows attackers to access unintended files when a filename prefix matches an allowed directory, potentially exposing sensitive data or system files outside the intended access boundaries.

The Model Context Protocol Servers project provides reference implementations for MCP, which enables AI models to interact with external systems and data sources. The Filesystem server component is designed to provide controlled file system access, but this vulnerability undermines those access controls.

Critical Impact

Attackers can bypass directory access restrictions to read files outside of intended allowed directories, potentially exposing sensitive configuration files, credentials, or other protected data.

Affected Products

• Model Context Protocol Servers Filesystem versions prior to 0.6.4
• Model Context Protocol Servers Filesystem versions prior to 2025.7.01

Discovery Timeline

• 2025-07-02 - CVE CVE-2025-53110 published to NVD
• 2025-07-03 - Last updated in NVD database

Technical Details for CVE-2025-53110

Vulnerability Analysis

This vulnerability is classified as CWE-22 (Improper Limitation of a Pathname to a Restricted Directory), commonly known as Path Traversal. The flaw exists in how the Filesystem server validates file paths against allowed directories.

When the MCP Filesystem server receives a request to access a file, it checks whether the requested path begins with an allowed directory prefix. However, the validation logic is flawed—it performs a simple string prefix match rather than a proper path canonicalization check. This means that if /allowed/dir is configured as an accessible directory, an attacker could potentially access /allowed/directory-secret or similar paths that share the same prefix but are outside the intended scope.

The network-accessible nature of this vulnerability, combined with the potential for accessing sensitive files across the system, makes this a significant security concern for organizations deploying MCP servers in production environments.

Root Cause

The root cause of this vulnerability lies in insufficient path validation within the Filesystem server component. The implementation uses a simple string prefix comparison to determine if a requested file path falls within allowed directories, rather than performing proper path normalization and directory containment checks.

Secure implementations should canonicalize paths (resolving symbolic links, .. sequences, and normalizing path separators) before comparing them against allowed directories, and should verify that the resolved path is actually contained within the allowed directory tree rather than merely sharing a prefix.

Attack Vector

The attack vector for CVE-2025-53110 is network-based, allowing remote attackers to exploit the vulnerability. An attacker with access to the MCP server interface can craft malicious file path requests that exploit the prefix-matching flaw.

The attack scenario involves:

1. The attacker identifies an allowed directory configured on the MCP Filesystem server (e.g., /data/public)
2. The attacker crafts a request for a path that shares the same prefix but extends beyond the allowed directory (e.g., /data/public-secrets/credentials.json)
3. Due to the flawed prefix validation, the server accepts the request and returns the contents of the unintended file

For detailed technical information about the vulnerability and the fix, refer to the GitHub Security Advisory GHSA-hc55-p739-j48w and the commit that addresses this issue.

Detection Methods for CVE-2025-53110

Indicators of Compromise

• Unusual file access patterns in MCP server logs showing requests to paths outside configured allowed directories
• Access attempts to sensitive system files such as /etc/passwd, configuration files, or credential stores through the MCP interface
• Log entries showing file paths that share prefixes with allowed directories but extend into adjacent directories
• Unexpected data exfiltration or file read operations originating from MCP server processes

Detection Strategies

• Implement file integrity monitoring (FIM) on sensitive directories that should not be accessible through MCP
• Monitor MCP server access logs for path patterns that indicate prefix exploitation attempts
• Deploy network traffic analysis to detect anomalous file content being transferred through MCP connections
• Configure security monitoring to alert on access to files containing sensitive keywords through MCP channels

Monitoring Recommendations

• Enable verbose logging on MCP Filesystem servers to capture all file access requests with full path details
• Implement centralized log collection for MCP servers and correlate access patterns across instances
• Set up alerting thresholds for file access requests that fall outside normal operational patterns
• Regularly audit allowed directory configurations to ensure they follow the principle of least privilege

How to Mitigate CVE-2025-53110

Immediate Actions Required

• Upgrade MCP Filesystem server to version 0.6.4 or 2025.7.01 immediately
• Audit existing MCP Filesystem configurations to identify potentially sensitive directories adjacent to allowed paths
• Review access logs for any historical evidence of exploitation attempts
• Consider temporarily restricting MCP Filesystem server access while performing the upgrade

Patch Information

The Model Context Protocol maintainers have released patched versions that address this path traversal vulnerability. Users should upgrade to one of the following versions:

• Version 0.6.4 - Semantic versioning track
• Version 2025.7.01 - Calendar versioning track

The fix is available in commit cc99bdabdcad93a58877c5f3ab20e21d4394423d. For complete details about the security issue and remediation guidance, see the GitHub Security Advisory GHSA-hc55-p739-j48w.

Workarounds

• If immediate patching is not possible, restrict network access to MCP Filesystem servers to trusted clients only
• Configure allowed directories with unique prefixes that do not share common paths with sensitive data
• Implement additional network-level access controls or authentication mechanisms in front of MCP servers
• Deploy a reverse proxy with path validation rules to filter potentially malicious requests before they reach the MCP server

# Example: Update MCP Filesystem server package
# Using npm (adjust based on your package manager)
npm update @modelcontextprotocol/server-filesystem

# Verify the installed version
npm list @modelcontextprotocol/server-filesystem
# Should show 0.6.4 or higher