CVE-2025-53899 Overview
CVE-2025-53899 affects Kiteworks Managed File Transfer (MFT), a platform that orchestrates end-to-end file transfer workflows. The back-end component contains an incorrectly specified destination in a communication channel [CWE-941]. An attacker with administrative privileges can intercept upstream communication under certain circumstances, leading to privilege escalation. Kiteworks patched the issue in version 9.1.0.
Critical Impact
An authenticated attacker with administrative privileges can intercept upstream traffic and escalate privileges, compromising confidentiality, integrity, and availability of the MFT system.
Affected Products
- Accellion Kiteworks Managed File Transfer versions prior to 9.1.0
- Kiteworks MFT back-end communication channel component
- Deployments using affected kiteworks_managed_file_transfer CPE configurations
Discovery Timeline
- 2025-11-29 - CVE-2025-53899 published to the National Vulnerability Database (NVD)
- 2025-12-03 - Last updated in NVD database
Technical Details for CVE-2025-53899
Vulnerability Analysis
The flaw stems from an incorrectly specified destination in a communication channel within the Kiteworks MFT back-end. The category corresponds to [CWE-941], where a product initiates an outbound communication to a destination that is not properly validated or specified. An attacker who already holds administrative privileges can manipulate or position themselves to receive upstream traffic that was intended for a different endpoint.
Because the back-end relies on the misconfigured channel for sensitive communication, intercepted traffic may include authentication material, session data, or workflow control messages. Reusing or replaying these artifacts allows the attacker to elevate effective privileges beyond their original administrative scope, potentially reaching system-level or cross-tenant access in multi-tenant deployments.
The vulnerability requires network reachability to the MFT back-end and valid administrative credentials. It does not require user interaction, and exploitation does not require complex preconditions once administrative access is obtained.
Root Cause
The root cause is improper validation of the destination endpoint in the back-end communication channel. The channel accepts or routes upstream traffic without strictly binding it to the intended recipient. Kiteworks addressed this by correcting the destination specification logic in version 9.1.0.
Attack Vector
Exploitation requires an attacker with administrative privileges on the Kiteworks MFT system and network access to the back-end. The attacker positions a controlled endpoint to receive upstream communication, captures sensitive traffic, and reuses the obtained data to escalate privileges. Refer to the Kiteworks Security Advisory GHSA-5gx5-vcpp-8cr5 for vendor technical details.
Detection Methods for CVE-2025-53899
Indicators of Compromise
- Unexpected outbound connections from the Kiteworks MFT back-end to non-approved hosts or network segments
- New or modified administrative accounts performing reconfiguration of communication endpoints
- Anomalous TLS sessions or plaintext flows originating from MFT back-end services
- Audit log entries showing changes to internal service endpoint configuration
Detection Strategies
- Baseline the expected destinations for Kiteworks MFT back-end traffic and alert on deviations
- Correlate administrative actions on the MFT console with subsequent network configuration or routing changes
- Inspect upstream traffic flows for redirection patterns inconsistent with the documented Kiteworks architecture
Monitoring Recommendations
- Forward Kiteworks MFT application and audit logs to a centralized SIEM for retention and correlation
- Monitor administrative authentication events and session activity for unusual source addresses or timing
- Track installed Kiteworks MFT versions across the environment to identify hosts still below 9.1.0
How to Mitigate CVE-2025-53899
Immediate Actions Required
- Upgrade all Kiteworks MFT instances to version 9.1.0 or later without delay
- Audit and reduce the number of accounts holding administrative privileges on the MFT system
- Rotate credentials, API keys, and service tokens used by the MFT back-end after patching
- Review network segmentation to ensure the MFT back-end is isolated from untrusted hosts
Patch Information
Kiteworks released a fix in version 9.1.0 that corrects the destination specification in the affected back-end communication channel. Vendor details are available in the Kiteworks Security Advisory GHSA-5gx5-vcpp-8cr5.
Workarounds
- Restrict administrative access to the MFT back-end using strict network ACLs and jump hosts
- Enforce multi-factor authentication for all administrative accounts on the Kiteworks platform
- Continuously monitor outbound destinations from the MFT back-end and block unapproved endpoints at the firewall
# Verify the installed Kiteworks MFT version is 9.1.0 or later
kiteworks-cli version
# Expected output: 9.1.0 or higher
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
