CVE-2025-53896: Kiteworks MFT Auth Bypass Vulnerability

CVE-2025-53896 Overview

CVE-2025-53896 is a session management vulnerability in Kiteworks Managed File Transfer (MFT) prior to version 9.1.0. The flaw causes active user sessions to remain valid past their inactivity timeout window under certain conditions. An attacker with access to a session token can continue operating against the application after the legitimate user has stopped interacting with it. The issue maps to CWE-613: Insufficient Session Expiration. Kiteworks patched the defect in release 9.1.0.

Critical Impact

A failure to terminate idle sessions extends the window for session hijacking, enabling unauthorized access to file transfer workflows and the data they handle.

Affected Products

• Accellion Kiteworks Managed File Transfer versions prior to 9.1.0
• Deployments exposing the Kiteworks web interface to authenticated users
• Environments relying on inactivity-based session expiration as a primary control

Discovery Timeline

• 2025-11-29 - CVE-2025-53896 published to NVD
• 2025-12-02 - Last updated in NVD database

Technical Details for CVE-2025-53896

Vulnerability Analysis

Kiteworks MFT orchestrates end-to-end file transfer workflows for enterprise users. The product enforces inactivity-based session expiration so that idle sessions cannot be reused indefinitely. In versions before 9.1.0, this control fails under specific conditions, allowing a session to remain authenticated past its intended timeout. An adversary who obtains a valid session identifier through token theft, shared workstation access, or browser artifact recovery can resume the session and interact with Kiteworks as the original user. The exploitation requires low-privilege authentication context but no user interaction, and the network attack surface includes any reachable Kiteworks endpoint.

Root Cause

The defect resides in the session lifecycle logic that tracks user activity and triggers expiration. Certain runtime conditions prevent the inactivity timer from invalidating the session server-side. The session token therefore continues to authenticate requests even after the inactivity threshold should have elapsed, violating the documented session policy.

Attack Vector

An attacker leverages an existing or captured session identifier against the Kiteworks MFT web interface. Because the server does not invalidate the idle session, requests bearing the token are accepted as authenticated. The attacker can list, download, upload, or modify files within the scope of the impersonated account. Confidentiality and integrity of transferred data are at risk, while availability is not directly affected. See the Kiteworks GitHub Security Advisory GHSA-23h2-3jj8-58hm for vendor-confirmed technical context.

Detection Methods for CVE-2025-53896

Indicators of Compromise

• Authenticated Kiteworks activity from a single session token spanning beyond the configured inactivity window
• Session reuse from a new source IP address or user agent without re-authentication
• File access or transfer events from accounts outside expected working hours

Detection Strategies

• Correlate Kiteworks authentication logs with session activity logs to identify sessions that persist past the inactivity threshold
• Flag concurrent or geographically inconsistent use of the same session identifier
• Baseline normal session durations per user and alert on outliers

Monitoring Recommendations

• Forward Kiteworks application and audit logs to a centralized SIEM for retention and correlation
• Monitor for anomalous file download volumes or transfer destinations associated with long-lived sessions
• Review administrative changes to session timeout configuration for unexpected modifications

How to Mitigate CVE-2025-53896

Immediate Actions Required

• Upgrade all Kiteworks MFT instances to version 9.1.0 or later
• Invalidate existing active sessions after patching to force re-authentication
• Audit recent session and file transfer activity for signs of misuse

Patch Information

Kiteworks resolved the issue in version 9.1.0. Refer to the Kiteworks Security Advisory GHSA-23h2-3jj8-58hm for vendor guidance and release details.

Workarounds

• Reduce the configured inactivity timeout to the lowest operationally acceptable value until patching is complete
• Enforce shorter absolute session lifetimes regardless of activity
• Require multi-factor authentication for all Kiteworks logins to limit the impact of token reuse
• Restrict Kiteworks administrative interfaces to trusted networks where feasible

# Configuration example
# Verify Kiteworks version after upgrade
kiteworks-cli system version
# Expected: 9.1.0 or higher