Unauthenticated Arbitrary File Write in Eclipse BaSyx Java Server SDK

Executive Summary

CVE-2026-57898 is a vulnerability in the Eclipse BaSyx Java Server SDK versions 2.0.0-milestone-05 to 2.0.0-milestone-12 when using the MongoDB backend. It allows an unauthenticated attacker to write arbitrary files to the server's filesystem through the AAS thumbnail API.

The vulnerability occurs because the thumbnail upload functionality accepts a client-controlled 'fileName' parameter. This parameter is used as both a repository key and a filesystem path without proper normalization or restriction. An attacker can exploit this by uploading thumbnail content with absolute or traversal-style filenames (e.g., '../../malicious_file'). When the thumbnail is retrieved, the uploaded content is written to the attacker-chosen path on the server.

This could lead to writing files anywhere the Java process has write permissions, potentially resulting in remote code execution. The default InMemory backend is not affected because it restricts file paths to a temporary directory.

The issue is fixed in Eclipse BaSyx Java Server SDK version 2.0.0-milestone-13.

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Detection Guidance

To detect this vulnerability on your network or system, you can follow these steps:

• Check if your deployment uses the Eclipse BaSyx Java Server SDK with the MongoDB backend. The vulnerability affects versions 2.0.0-milestone-05 to 2.0.0-milestone-12.
• Inspect the AAS thumbnail API endpoints for unusual file upload or retrieval activity. Look for requests containing absolute or traversal-style filenames (e.g., '../../malicious_file').
• Review server logs for unexpected file writes outside the intended temporary directory. Commands like 'grep' or log analysis tools can help identify suspicious file paths.
• Verify the installed version of the Eclipse BaSyx Java Server SDK. If it falls within the vulnerable range, assume the system is at risk. Example command to check version (if available in logs or package manager): 'grep -i "basyx.*version" /path/to/logs'.
• Use network scanning tools to detect exposed AAS thumbnail API endpoints. For example, tools like 'nmap' can help identify open ports or services associated with BaSyx deployments.

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Impact Analysis

If you are using an affected version of the Eclipse BaSyx Java Server SDK with the MongoDB backend, this vulnerability could have severe consequences for your system and organization.

• Unauthorized file writes: An attacker can write arbitrary files to any location on the server where the Java process has write permissions. This could include sensitive system directories or application directories.
• Remote code execution: By writing malicious files (e.g., web shells, scripts, or executables), an attacker could gain control over the server, execute arbitrary commands, or escalate privileges.
• Data breaches: Attackers could overwrite or corrupt critical data files, leading to data loss or unauthorized access to sensitive information.
• System compromise: The server could be used as a pivot point for further attacks within your network, compromising other systems or services.
• Service disruption: Attackers could overwrite or delete critical system files, causing downtime or rendering the server inoperable.

The vulnerability is particularly dangerous because it does not require authentication, meaning any remote attacker with access to the API can exploit it.

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Compliance Impact

This vulnerability can significantly impact compliance with various standards and regulations, depending on the nature of the data and systems involved.

• GDPR (General Data Protection Regulation): If the affected system processes or stores personal data of EU citizens, this vulnerability could lead to a data breach. Unauthorized file writes could expose or alter personal data, violating GDPR's requirements for data protection and integrity. This could result in hefty fines (up to 4% of global revenue or €20 million, whichever is higher) and reputational damage.
• HIPAA (Health Insurance Portability and Accountability Act): For organizations handling protected health information (PHI), this vulnerability could lead to unauthorized access or modification of PHI. This violates HIPAA's Security Rule, which requires safeguards to ensure the confidentiality, integrity, and availability of PHI. Non-compliance can result in fines ranging from $100 to $50,000 per violation, with a maximum of $1.5 million per year.
• PCI DSS (Payment Card Industry Data Security Standard): If the affected system processes, stores, or transmits payment card data, this vulnerability could lead to unauthorized access or modification of cardholder data. This violates multiple PCI DSS requirements, including those related to secure systems and data protection. Non-compliance can result in fines, increased transaction fees, or loss of the ability to process payment cards.
• ISO 27001: This standard requires organizations to implement controls to manage information security risks. The vulnerability represents a failure to adequately protect against unauthorized access or modification of information, which could lead to non-compliance with ISO 27001 requirements. This could affect certification status and business relationships that require ISO 27001 compliance.
• SOC 2: For service organizations, this vulnerability could impact compliance with SOC 2's Trust Services Criteria, particularly the Security, Availability, and Confidentiality principles. A successful exploit could lead to unauthorized access, data breaches, or service disruptions, potentially resulting in a failed SOC 2 audit.

In all cases, the vulnerability could lead to a loss of trust from customers, partners, and regulators, as well as potential legal liabilities if sensitive data is compromised.

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Mitigation Strategies

To mitigate this vulnerability, take the following immediate steps:

• Upgrade the Eclipse BaSyx Java Server SDK to version 2.0.0-milestone-13 or later, as the issue is fixed in this release.
• If upgrading is not immediately possible, disable the AAS thumbnail API or restrict access to it using network-level controls (e.g., firewalls, access control lists).
• Switch from the MongoDB backend to the default InMemory backend, which is not affected by this vulnerability due to its path normalization and restriction mechanisms.
• Monitor the server filesystem for unauthorized file writes, especially in sensitive directories. Use tools like 'auditd' or file integrity monitoring (FIM) solutions to detect suspicious activity.
• Review and restrict the permissions of the Java process to minimize the impact of any potential file writes. Ensure the process does not have unnecessary write access to critical directories.
• Implement input validation and sanitization for the 'fileName' parameter in the AAS thumbnail API to prevent path traversal or absolute path attacks.

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