CVE-2025-47792 is a medium-severity vulnerability classified under CWE-284 (Improper Access Control) affecting Nextcloud Desktop versions prior to 3.15. Nextcloud Desktop is a widely used client application that synchronizes files between a user's local machine and a Nextcloud server. The vulnerability arises from the socket API exposed by the Nextcloud Desktop client, which allows third-party applications already installed on the user's machine to create link shares for nearly all data synchronized by Nextcloud Desktop. This means that malicious or compromised local applications can programmatically generate shareable links to user files without proper authorization checks. These links can then be exfiltrated to external services, potentially leaking sensitive or confidential data. The vulnerability requires local access with low privileges (PR:L) and user interaction (UI:R) to exploit, and the attack vector is local (AV:L), meaning the attacker must have some presence on the user's machine. The vulnerability impacts confidentiality severely (C:H), with limited impact on integrity (I:L) and no impact on availability (A:N). Nextcloud Desktop version 3.15 and later have addressed this issue by implementing stricter access controls on the socket API to prevent unauthorized link share creation. No known workarounds exist, so upgrading to version 3.15 or later is the primary remediation. There are no known exploits in the wild at the time of publication. This vulnerability highlights the risk of insufficient access control on inter-process communication interfaces, especially for applications handling sensitive user data.

For European organizations, this vulnerability poses a significant risk to data confidentiality, especially for entities relying on Nextcloud Desktop for secure file synchronization and sharing. Sensitive corporate or personal data could be exposed if a malicious local application or insider threat exploits this flaw to create unauthorized share links and exfiltrate data. This could lead to data breaches, regulatory non-compliance (e.g., GDPR violations), reputational damage, and potential financial penalties. The requirement for local access and user interaction somewhat limits remote exploitation but does not eliminate risk, particularly in environments where endpoint security is weak or where users may inadvertently install malicious software. Organizations with distributed workforces using Nextcloud Desktop on personal or corporate devices are particularly vulnerable. The vulnerability also raises concerns about insider threats or compromised endpoints within secure networks. Given the widespread use of Nextcloud in European public and private sectors, the impact could be broad if not mitigated promptly.

1. Immediate upgrade of Nextcloud Desktop clients to version 3.15 or later to ensure the vulnerability is patched. 2. Implement strict endpoint security controls to prevent installation or execution of unauthorized third-party applications that could exploit the socket API. 3. Employ application whitelisting and robust anti-malware solutions to detect and block suspicious local processes attempting to interact with Nextcloud Desktop. 4. Educate users about the risks of installing untrusted software and the importance of reporting unusual application behavior. 5. Monitor network traffic for unusual outbound connections that could indicate exfiltration of shared links. 6. Restrict local user privileges where possible to limit the ability of low-privilege applications to interact with Nextcloud Desktop. 7. Consider deploying host-based intrusion detection systems (HIDS) to detect anomalous inter-process communications related to Nextcloud Desktop. 8. Review and tighten Nextcloud server-side sharing policies to limit the scope and lifetime of shareable links, reducing potential exposure if a link is created maliciously.