CVE-2025-14199: Verysync RCE Vulnerability

CVE-2025-14199 Overview

A security vulnerability has been identified in Verysync (微力同步) up to version 2.21.3 that allows unrestricted file upload through the Web Administration Module. The flaw exists in the file handling function accessible via the /rest/f/api/resources/f96956469e7be39d/tmp/text.txt?override=false endpoint. An authenticated attacker can exploit this vulnerability remotely to upload arbitrary files to the affected system, potentially leading to further compromise.

Critical Impact
This unrestricted file upload vulnerability could allow attackers to upload malicious files, including web shells or executable content, potentially leading to remote code execution or system compromise.

Affected Products

Verysync (微力同步) versions up to and including 2.21.3
Verysync Web Administration Module

Discovery Timeline

2025-12-07 - CVE-2025-14199 published to NVD
2025-12-11 - Last updated in NVD database

Technical Details for CVE-2025-14199

Vulnerability Analysis

This vulnerability is classified under CWE-434 (Unrestricted Upload of File with Dangerous Type) and CWE-284 (Improper Access Control). The affected component is the Web Administration Module of Verysync, which fails to properly validate and restrict file uploads through its REST API endpoint.

The vulnerability allows authenticated users to upload files without proper validation of file types, content, or destination. The API endpoint /rest/f/api/resources/f96956469e7be39d/tmp/text.txt?override=false does not implement adequate security controls to prevent the upload of potentially dangerous file types. This improper access control combined with the unrestricted upload capability creates a significant security risk for organizations running affected versions of Verysync.

The vendor was contacted about this vulnerability but did not respond, and an exploit has been publicly disclosed, increasing the risk of exploitation in the wild.

Root Cause

The root cause of this vulnerability stems from insufficient input validation and access control mechanisms in the Verysync Web Administration Module. The application fails to:

Properly validate uploaded file types against an allowlist
Implement content-type verification to ensure uploaded files match their declared types
Restrict the upload destination to prevent arbitrary file placement
Apply appropriate access controls to the file upload functionality

Attack Vector

The attack can be performed remotely over the network by an authenticated user. An attacker with low-privilege access to the Verysync Web Administration Module can exploit this vulnerability by sending crafted HTTP requests to the vulnerable REST API endpoint. The attack does not require user interaction and can be automated.

The exploitation process involves sending malicious file content to the /rest/f/api/resources/f96956469e7be39d/tmp/text.txt?override=false endpoint, bypassing insufficient file type restrictions to upload arbitrary content to the server.

For detailed technical information about this vulnerability, refer to the GitHub Issue Report and VulDB Entry #334619.

Detection Methods for CVE-2025-14199

Indicators of Compromise

Unusual HTTP POST requests to /rest/f/api/resources/*/tmp/* endpoints on Verysync servers
Presence of unexpected or malicious files in Verysync temporary or web-accessible directories
Web shell indicators or executable files appearing in directories managed by Verysync
Anomalous outbound network connections originating from Verysync server processes

Detection Strategies

Monitor HTTP access logs for suspicious requests targeting the /rest/f/api/resources/ endpoint with file upload operations
Implement file integrity monitoring on Verysync installation directories to detect unauthorized file additions
Deploy web application firewall (WAF) rules to detect and block attempts to upload potentially dangerous file types
Review authentication logs for unusual access patterns to the Web Administration Module

Monitoring Recommendations

Enable verbose logging for the Verysync Web Administration Module and regularly audit access patterns
Configure alerts for any file upload activity to sensitive directories
Implement network segmentation to limit access to Verysync administrative interfaces
Deploy endpoint detection and response (EDR) solutions to detect post-exploitation activity

How to Mitigate CVE-2025-14199

Immediate Actions Required

Restrict network access to the Verysync Web Administration Module to trusted IP addresses only
Review and audit all user accounts with access to the administrative interface
Implement additional authentication controls such as multi-factor authentication
Scan affected systems for any indicators of compromise or unauthorized file uploads

Patch Information

As of the last NVD update on 2025-12-11, no official patch has been released by the vendor. The vendor was contacted about this disclosure but did not respond. Organizations should monitor the official Verysync channels for security updates and apply patches immediately when available.

For additional technical details and tracking, refer to the VulDB CTI entry and VulDB submission.

Workarounds

Disable or restrict access to the Web Administration Module until a patch is available
Implement network-level access controls (firewall rules, VPN requirements) to limit exposure of the Verysync administrative interface
Deploy a reverse proxy with request filtering capabilities to block suspicious file upload attempts
Consider temporarily disabling the affected file upload functionality if operationally feasible

bash

# Example: Restrict access to Verysync admin interface via iptables
# Allow only trusted management subnet
iptables -A INPUT -p tcp --dport 8886 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 8886 -j DROP