CVE-2025-53109 is a high-severity vulnerability classified under CWE-59: Improper Link Resolution Before File Access ('Link Following') affecting the Model Context Protocol (MCP) Servers, specifically versions of the Filesystem component prior to 0.6.4 or 2025.7.01. MCP Servers are reference implementations used to handle model context protocols, which likely involve structured data or configuration management. The vulnerability arises when the server improperly resolves symbolic links (symlinks) within directories that are otherwise allowed for access. This improper resolution allows an attacker to craft symlinks that point to unintended files outside the permitted directory scope, potentially exposing sensitive files or enabling unauthorized file access. The CVSS 4.0 score of 7.3 reflects a high severity, with network attack vector (AV:N), low attack complexity (AC:L), partial attack traceability (AT:P), no privileges required (PR:N), user interaction required (UI:P), and high impact on availability (VA:H), integrity (VI:N), and confidentiality (VC:N). The scope is high (S:H), indicating that the vulnerability affects components beyond the initially vulnerable scope, and the security requirements for confidentiality, integrity, and availability are all high (SC:H, SI:H, SA:H). Although no known exploits are currently reported in the wild, the nature of the vulnerability suggests that exploitation could lead to unauthorized disclosure or modification of critical files, potentially compromising system stability or confidentiality. The vulnerability can be mitigated by upgrading to the fixed versions 0.6.4 or 2025.7.01, which presumably include proper symlink resolution checks to prevent traversal outside allowed directories.

For European organizations, this vulnerability poses significant risks, especially for those relying on MCP Servers for critical infrastructure, data modeling, or configuration management. Unauthorized file access via symlink exploitation could lead to exposure of sensitive configuration files, credentials, or intellectual property. This could result in data breaches, disruption of services, or unauthorized system modifications. Given the high availability impact, exploitation might also cause denial of service or system instability. Organizations in sectors such as finance, healthcare, manufacturing, and government, which often use specialized protocols and reference implementations like MCP, could face operational disruptions and regulatory compliance issues under GDPR if personal or sensitive data is exposed. The requirement for user interaction lowers the risk somewhat but does not eliminate it, as social engineering or phishing could facilitate exploitation. The lack of required privileges means that even unprivileged users or external attackers could attempt exploitation remotely, increasing the threat surface.

Beyond upgrading to the patched versions 0.6.4 or 2025.7.01, European organizations should implement strict file system access controls and monitoring to detect unusual symlink creation or access patterns. Employing application-level whitelisting for file paths and enforcing least privilege principles on services running MCP Servers can reduce exploitation risk. Regularly auditing file system permissions and symlink usage within allowed directories can help identify potential attack vectors. Network segmentation and firewall rules should limit access to MCP Server endpoints to trusted users and systems only. Additionally, user awareness training to recognize social engineering attempts can mitigate the user interaction requirement for exploitation. Implementing runtime application self-protection (RASP) or file integrity monitoring (FIM) tools can provide real-time detection of unauthorized file access attempts. Finally, maintaining an incident response plan that includes procedures for symlink-related attacks will improve organizational resilience.