CVE-2025-53939 Overview
CVE-2025-53939 affects Kiteworks, a private data network (PDN) platform developed by Accellion. The vulnerability stems from improper input validation when managing roles of a shared folder. An authenticated attacker can exploit this flaw to unexpectedly elevate another user's permissions on a shared folder. The issue impacts all Kiteworks versions prior to 9.1.0 and has been patched in version 9.1.0. The flaw is classified under [CWE-20] (Improper Input Validation) and carries a network-based attack vector with low privileges required.
Critical Impact
An authenticated low-privileged user can manipulate shared folder role assignments to escalate another user's permissions, resulting in unauthorized access to confidential data and potential integrity compromise within the Kiteworks private data network.
Affected Products
- Accellion Kiteworks versions prior to 9.1.0
- Kiteworks Private Data Network (PDN) deployments using shared folder functionality
- All deployment modes (on-premises, cloud, hybrid) running affected versions
Discovery Timeline
- 2025-11-29 - CVE-2025-53939 published to the National Vulnerability Database
- 2025-12-04 - Last updated in NVD database
Technical Details for CVE-2025-53939
Vulnerability Analysis
The vulnerability resides in the shared folder role management functionality of Kiteworks. When a user with permission to manage a shared folder submits role change requests, the application fails to properly validate the input parameters governing role assignments. This validation gap allows an attacker to manipulate the role management workflow and assign elevated permissions to another user account on a shared folder. Because Kiteworks is designed to handle sensitive file transfer and collaboration workloads, unauthorized permission elevation directly exposes confidential business data. The vulnerability requires authentication but does not require user interaction from the victim, and it is exploitable over the network through the Kiteworks web interface or API.
Root Cause
The root cause is improper input validation [CWE-20] in the role management endpoint for shared folders. The application accepts role modification parameters without sufficiently verifying the relationship between the requester's privileges and the target permission level being assigned. This validation gap creates a horizontal-to-vertical privilege escalation primitive within the sharing model.
Attack Vector
An authenticated attacker with low privileges interacts with the shared folder role management feature and submits crafted role assignment requests. Because input validation is insufficient, the request succeeds in granting another user elevated permissions beyond what the access control model intends. The resulting state grants the colluding or attacker-controlled account read, write, or administrative access to the shared folder contents. See the Kiteworks Security Advisory GHSA-hpf5-6376-2565 for vendor-provided technical details.
Detection Methods for CVE-2025-53939
Indicators of Compromise
- Unexpected role or permission changes on shared folders in Kiteworks audit logs
- Users gaining access to shared folders without a corresponding legitimate invitation or admin action
- API calls to shared folder role management endpoints from low-privileged accounts that result in elevated role assignments
- Anomalous access patterns where users open or download files from folders they previously had no access to
Detection Strategies
- Review Kiteworks audit logs for role modification events and correlate them against approved change requests
- Baseline normal sharing activity per user and alert on outliers in permission grants per session
- Monitor administrative and API endpoints handling shared folder roles for repeated or malformed requests
Monitoring Recommendations
- Forward Kiteworks application and audit logs to a centralized logging or SIEM platform for retention and correlation
- Alert on changes to folder ownership, manager roles, or downloader roles that occur outside of change management windows
- Track first-time accesses to high-value shared folders, particularly from accounts recently granted permissions
How to Mitigate CVE-2025-53939
Immediate Actions Required
- Upgrade Kiteworks to version 9.1.0 or later, which contains the official fix for CVE-2025-53939
- Audit existing shared folder role assignments to identify any unauthorized elevations performed prior to patching
- Revoke unexpected permissions and reset role assignments on sensitive shared folders
- Enforce least privilege for Kiteworks user accounts and review delegation of shared folder management rights
Patch Information
Accellion released the fix in Kiteworks version 9.1.0. Administrators should consult the Kiteworks Security Advisory GHSA-hpf5-6376-2565 for upgrade guidance and version-specific instructions. There is no vendor-supplied workaround that fully addresses the input validation flaw, so upgrading is the required remediation.
Workarounds
- Restrict shared folder management permissions to a minimal set of trusted administrators until the patch is applied
- Disable or limit external sharing on highly sensitive folders during the remediation window
- Increase audit log review frequency and require manual approval for role escalations on regulated data repositories
# Verify the running Kiteworks version and confirm it is 9.1.0 or later
kiteworks-cli system version
# Example: export shared folder permissions for review prior to upgrade
kiteworks-cli folders export-permissions --output /tmp/kw-folder-perms.csv
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
