CVE-2025-53109 in server-filesystem
Summary
by MITRE • 07/02/2025
Model Context Protocol Servers is a collection of reference implementations for the model context protocol (MCP). Versions of Filesystem prior to 0.6.4 or 2025.7.01 could allow access to unintended files via symlinks within allowed directories. Users are advised to upgrade to 0.6.4 or 2025.7.01 resolve.
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Analysis
by VulDB Data Team • 07/02/2025
The Model Context Protocol Servers represents a critical security vulnerability affecting filesystem implementations within the Model Context Protocol ecosystem. This vulnerability specifically targets versions prior to 064 or 2025701 where the filesystem component fails to properly validate symbolic link traversals within allowed directories. The flaw creates an unintended access pathway that allows malicious actors to bypass directory restrictions and gain access to files outside of the intended scope. This represents a fundamental breakdown in access control mechanisms that should have prevented such lateral movement within the filesystem hierarchy.
The technical implementation of this vulnerability stems from insufficient symlink validation during file access operations. When a user or application requests access to a file within an allowed directory, the system should verify that the requested path does not contain symbolic links that point outside of the permitted boundaries. However, in affected versions, the system processes symbolic links without proper resolution checks, allowing attackers to craft requests that traverse beyond the intended directory scope. This flaw operates at the core of file system access control and represents a classic case of insufficient input validation and path traversal vulnerability.
The operational impact of this vulnerability extends beyond simple unauthorized file access, creating potential for data exfiltration, privilege escalation, and system compromise. An attacker exploiting this vulnerability could access sensitive configuration files, user data, or system binaries that should remain protected within restricted directories. The vulnerability is particularly concerning in environments where multiple users or applications share filesystem resources, as it could enable lateral movement and information disclosure across different security domains. This type of vulnerability aligns with CWE-367, which addresses time-of-check to time-of-use (TOCTOU) race conditions, and represents a specific implementation weakness in path validation controls.
Mitigation strategies should prioritize immediate upgrade to version 0.6.4 or 2025.7.01 where the vulnerability has been addressed through proper symlink validation mechanisms. Organizations should also implement additional monitoring for suspicious file access patterns and consider implementing stricter access controls at the filesystem level. The fix implemented in the updated versions likely includes enhanced path resolution logic that prevents symbolic link traversal beyond designated boundaries, aligning with best practices for secure file system access control as recommended by the CWE guidelines. Security teams should conduct thorough testing of the updated implementations to ensure that the fix does not introduce regressions while maintaining proper access control functionality across all supported environments.