CVE-2025-53939 is a vulnerability identified in the Kiteworks private data network (PDN) product, specifically in versions prior to 9.1.0. The root cause is improper input validation (CWE-20) during the management of roles assigned to shared folders. This flaw allows an attacker with low privileges to manipulate role assignments, resulting in the unexpected elevation of permissions for other users on the same shared folder. The vulnerability is exploitable remotely over the network (AV:N), requires low attack complexity (AC:L), and only low privileges (PR:L) without any user interaction (UI:N). The scope is unchanged (S:U), but the impact affects confidentiality, integrity, and availability to a limited extent (C:L/I:L/A:L). By exploiting this vulnerability, an attacker could gain unauthorized access to sensitive data or perform unauthorized actions within shared folders, potentially leading to data leakage or disruption of data availability. The issue has been addressed and patched in Kiteworks version 9.1.0. No public exploits have been reported to date, but the vulnerability's nature makes it a significant risk for organizations relying on Kiteworks for secure data sharing.

For European organizations, this vulnerability poses a risk of unauthorized data access and privilege escalation within shared data environments. Given Kiteworks' role in secure data exchange, exploitation could lead to exposure of sensitive or regulated information, violating data protection regulations such as GDPR. The integrity of shared data could be compromised, and availability disrupted if attackers manipulate permissions to deny legitimate access. Organizations in sectors handling confidential data—such as finance, healthcare, legal, and government—are particularly vulnerable. The medium CVSS score reflects a moderate but tangible risk that could facilitate insider threats or lateral movement by attackers. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially as attackers often develop exploits post-disclosure. Failure to patch could result in compliance issues and reputational damage if data breaches occur.

European organizations should immediately assess their Kiteworks deployments and verify the version in use. Upgrading to Kiteworks version 9.1.0 or later is the primary and most effective mitigation. Until patched, organizations should restrict network access to the Kiteworks management interfaces to trusted administrators only, employing network segmentation and strict firewall rules. Implement robust monitoring and logging of role management activities to detect anomalous permission changes. Enforce the principle of least privilege for all users managing shared folder roles. Conduct regular audits of shared folder permissions to identify and remediate unauthorized escalations. Additionally, integrate Kiteworks access controls with centralized identity and access management (IAM) solutions to enhance oversight. Finally, maintain up-to-date incident response plans to quickly address any exploitation attempts.