CVE-2025-56869 is a directory traversal vulnerability identified in the Sync In server software, specifically affecting versions up to 1.1.1. The vulnerability exists in two backend service functions: FilesManager.saveMultipart and FilesManager.compress, located in the files-manager.service.ts source file. These functions are responsible for handling file operations such as saving multipart file uploads and compressing files. Due to insufficient validation or sanitization of file path inputs, authenticated attackers can exploit this flaw to perform directory traversal attacks. This allows them to read from and write to arbitrary locations on the server's filesystem beyond the intended directories. Such unauthorized access can lead to exposure of sensitive data, modification or insertion of malicious files, and potentially compromise the integrity and availability of the system. The vulnerability requires authentication, meaning the attacker must have valid credentials or access to an account on the Sync In server. However, once authenticated, the attacker can leverage this flaw to escalate their privileges by manipulating file storage and compression operations. No CVSS score has been assigned yet, and there are no known exploits in the wild at the time of publication. The lack of patch links suggests that a fix may not have been released or publicly disclosed yet. Given the nature of directory traversal vulnerabilities, this issue poses a significant risk to the confidentiality and integrity of data managed by the Sync In server.

For European organizations using the Sync In server, this vulnerability could have serious consequences. Unauthorized read access could expose sensitive corporate or personal data, potentially violating GDPR and other data protection regulations, leading to legal and financial penalties. Write access could allow attackers to implant malicious files, such as web shells or ransomware payloads, enabling further compromise or disruption of business operations. The requirement for authentication limits exposure to internal or compromised users, but insider threats or credential theft could facilitate exploitation. Organizations relying on Sync In for file synchronization and storage may face operational disruptions if critical files are altered or deleted. Additionally, the breach of data confidentiality and integrity could damage organizational reputation and trust with customers and partners. The absence of a patch increases the urgency for organizations to implement compensating controls to mitigate risk until an official fix is available.

European organizations should take immediate steps to mitigate this vulnerability. First, restrict access to the Sync In server to trusted users and networks, employing network segmentation and firewall rules to limit exposure. Implement strong authentication mechanisms, including multi-factor authentication, to reduce the risk of credential compromise. Monitor logs for unusual file access patterns or attempts to exploit file upload and compression features. Employ application-layer filtering or web application firewalls (WAFs) to detect and block directory traversal payloads targeting the vulnerable functions. Until a patch is available, consider disabling or restricting the FilesManager.saveMultipart and FilesManager.compress functionalities if feasible. Conduct regular audits of file system integrity and backups to detect unauthorized changes promptly. Finally, maintain close communication with the vendor or open-source community for updates and apply patches as soon as they are released.