CVE-2026-6105: go-fastdfs-web Auth Bypass Vulnerability

CVE-2026-6105 Overview

A security vulnerability has been identified in perfree go-fastdfs-web up to version 1.3.7. This affects an unknown part of the file src/main/java/com/perfree/controller/InstallController.java of the component doInstall Interface. The manipulation leads to improper authorization, allowing unauthorized access to installation functionality. The attack may be initiated remotely, and the exploit has been disclosed publicly and may be used. The vendor was contacted early about this disclosure but did not respond in any way.

Critical Impact

Remote attackers can exploit improper authorization in the doInstall interface to potentially reconfigure or reinstall the application without proper authentication, leading to system compromise, data loss, or service disruption.

Affected Products

• perfree go-fastdfs-web versions up to 1.3.7
• InstallController.java doInstall Interface component

Discovery Timeline

• April 11, 2026 - CVE-2026-6105 published to NVD
• April 13, 2026 - Last updated in NVD database

Technical Details for CVE-2026-6105

Vulnerability Analysis

This vulnerability is classified as CWE-266 (Incorrect Privilege Assignment), which occurs when a product incorrectly assigns a privilege to a particular actor, creating an unintended sphere of control for that actor. In the context of go-fastdfs-web, the InstallController.java component fails to properly verify authorization before allowing access to the doInstall interface.

The vulnerability resides in the installation controller, which typically handles initial application setup and configuration. When authorization checks are missing or improperly implemented, attackers can invoke installation routines even after the application has been deployed and configured. This can lead to unauthorized reconfiguration of the system, potentially overwriting existing settings, database connections, or administrative credentials.

The network-accessible nature of this vulnerability means that any attacker with network access to the affected web application can potentially exploit this flaw without requiring prior authentication or special privileges.

Root Cause

The root cause of this vulnerability is improper authorization implementation in the InstallController.java file. The doInstall interface lacks adequate access control mechanisms to verify whether the requesting user has the necessary privileges to perform installation operations. This represents a classic authorization bypass where sensitive administrative functionality is exposed without proper authentication or privilege verification.

Installation endpoints are particularly sensitive because they often allow setting up database connections, creating administrative accounts, and configuring system parameters. When these endpoints remain accessible after initial setup, they create a significant security risk.

Attack Vector

The attack vector for CVE-2026-6105 is network-based, requiring no user interaction and no prior authentication. An attacker can remotely access the vulnerable doInstall interface by sending crafted HTTP requests to the affected endpoint.

The exploitation process involves identifying the target go-fastdfs-web installation and directly accessing the installation controller endpoint. Since proper authorization checks are not enforced, the attacker can invoke the installation functionality to potentially reset the application configuration, modify database settings, or create new administrative accounts with attacker-controlled credentials.

For detailed technical information about the exploit, refer to the Gitee CVE Issue Discussion and VulDB Vulnerability #356964.

Detection Methods for CVE-2026-6105

Indicators of Compromise

• Unexpected HTTP requests to /install or doInstall endpoints after initial application deployment
• Unauthorized changes to application configuration or database connection settings
• Creation of new administrative accounts without legitimate administrator action
• Application reinstallation or reset events in system logs
• Anomalous access patterns to InstallController endpoints from external IP addresses

Detection Strategies

• Implement web application firewall (WAF) rules to block unauthorized access to installation endpoints
• Monitor HTTP access logs for requests targeting InstallController.java related endpoints
• Configure intrusion detection systems (IDS) to alert on installation endpoint access patterns
• Review application logs for unauthorized configuration changes or reinstallation attempts

Monitoring Recommendations

• Enable detailed logging for all administrative and installation-related endpoints
• Set up alerts for any access attempts to installation interfaces in production environments
• Monitor for changes to application configuration files and database schemas
• Implement file integrity monitoring on critical configuration files
• Review authentication logs for failed or bypassed authorization events

How to Mitigate CVE-2026-6105

Immediate Actions Required

• Restrict network access to the go-fastdfs-web installation endpoints using firewall rules
• Implement additional authentication checks at the web server or reverse proxy level for installation URLs
• Review and audit any configuration changes that may have occurred due to exploitation
• Consider taking the application offline if compromise is suspected until proper remediation is in place
• Monitor for any indicators of compromise as detailed above

Patch Information

At the time of this advisory, no official patch has been released by the vendor. The vendor was contacted early about this disclosure but did not respond in any way. Users should monitor the VulDB Submission #781598 and official project repositories for updates regarding security patches.

In the absence of an official fix, organizations should implement the workarounds described below and consider the risk of continuing to use affected versions of the software.

Workarounds

• Disable or remove the InstallController.java component if the application has already been installed and configured
• Implement reverse proxy rules (nginx, Apache) to block access to /install and related endpoints
• Add IP-based access restrictions to limit installation endpoint access to trusted administrative networks only
• Deploy web application firewall (WAF) rules to detect and block exploitation attempts
• Consider migrating to alternative software if security updates are not forthcoming from the vendor

# Example nginx configuration to block access to install endpoints
location ~ ^/install {
    deny all;
    return 403;
}

# Alternative: Restrict to specific admin IP addresses
location ~ ^/install {
    allow 192.168.1.100;  # Admin IP
    deny all;
}