CVE-2026-5261: Shandong Hoteam InforCenter PLM RCE Flaw

CVE-2026-5261 Overview

A vulnerability has been identified in Shandong Hoteam InforCenter PLM up to version 8.3.8 that allows unrestricted file upload through the uploadFileToIIS function. The affected component is located in the file /Base/BaseHandler.ashx, and manipulation of the File argument enables attackers to upload arbitrary files to the server. This vulnerability can be exploited remotely without authentication, and a public exploit is available. The vendor was contacted about this disclosure but did not respond.

Critical Impact

Remote attackers can upload malicious files to the server, potentially leading to remote code execution, web shell deployment, or complete system compromise.

Affected Products

• Shandong Hoteam InforCenter PLM up to version 8.3.8
• Systems running /Base/BaseHandler.ashx handler
• IIS-based deployments of InforCenter PLM

Discovery Timeline

• April 1, 2026 - CVE-2026-5261 published to NVD
• April 1, 2026 - Last updated in NVD database

Technical Details for CVE-2026-5261

Vulnerability Analysis

This unrestricted file upload vulnerability (CWE-284: Improper Access Control) exists in the uploadFileToIIS function within the /Base/BaseHandler.ashx handler. The application fails to properly validate or restrict the types of files that can be uploaded through this endpoint. When an attacker manipulates the File argument, they can bypass any intended restrictions and upload arbitrary files to the server's file system.

The vulnerability is particularly concerning because it can be exploited remotely without any authentication requirements. An attacker simply needs network access to the vulnerable endpoint to initiate an attack. The public availability of exploit details increases the risk of widespread exploitation.

Root Cause

The root cause of this vulnerability is improper access control in the file upload functionality. The uploadFileToIIS function does not implement adequate validation checks on uploaded files. This includes:

• Missing or insufficient file type validation
• Lack of file extension whitelisting
• Absence of content-type verification
• No authentication or authorization requirements for the upload endpoint

Attack Vector

The attack can be initiated remotely over the network. An attacker targets the /Base/BaseHandler.ashx endpoint and manipulates the File parameter to upload malicious content. Since no authentication is required and the attack complexity is low, this vulnerability is accessible to a wide range of threat actors.

The attacker can craft HTTP requests to the vulnerable handler, including malicious payloads such as web shells (e.g., ASPX files), executable content, or other dangerous file types. Once uploaded, these files may be executed by the server or accessed directly, enabling further compromise of the system.

For detailed technical information about this vulnerability, refer to the VulDB Vulnerability Entry or the original disclosure documentation.

Detection Methods for CVE-2026-5261

Indicators of Compromise

• Suspicious HTTP POST requests to /Base/BaseHandler.ashx with file upload parameters
• Unexpected files appearing in web-accessible directories, particularly ASPX, ASP, or other executable file types
• Web server logs showing repeated access to the uploadFileToIIS function from external IP addresses
• New or modified files in IIS upload directories with recent timestamps

Detection Strategies

• Monitor HTTP traffic for POST requests to /Base/BaseHandler.ashx containing file attachments
• Implement file integrity monitoring on web server directories to detect unauthorized file additions
• Configure web application firewall (WAF) rules to inspect and block suspicious file uploads
• Review IIS logs for anomalous patterns of requests to the vulnerable endpoint

Monitoring Recommendations

• Enable detailed logging for the /Base/BaseHandler.ashx endpoint
• Set up alerts for file creation events in web-accessible directories
• Monitor for execution of newly created files on the web server
• Implement network-level monitoring for traffic patterns consistent with exploitation attempts

How to Mitigate CVE-2026-5261

Immediate Actions Required

• Restrict network access to the /Base/BaseHandler.ashx endpoint using firewall rules or access control lists
• Implement authentication requirements for all file upload functionality
• Add file type validation and whitelist only necessary file extensions
• Consider temporarily disabling the uploadFileToIIS function if not critical to operations

Patch Information

No official patch information is currently available from the vendor. According to the disclosure, the vendor (Shandong Hoteam) was contacted but did not respond. Organizations should monitor the VulDB entry for updates and apply any future patches as soon as they become available.

Workarounds

• Deploy a web application firewall (WAF) with rules to block malicious file uploads to the vulnerable endpoint
• Implement network segmentation to limit access to the PLM system from untrusted networks
• Add server-side validation to restrict uploaded files to specific, safe file types
• Configure IIS to prevent execution of uploaded files by setting appropriate handler mappings
• Consider using reverse proxy configurations to add additional authentication layers

# Example IIS configuration to restrict handler access
# Add to web.config in application root
# <location path="Base/BaseHandler.ashx">
#   <system.webServer>
#     <security>
#       <ipSecurity allowUnlisted="false">
#         <add ipAddress="10.0.0.0" subnetMask="255.0.0.0" allowed="true"/>
#       </ipSecurity>
#     </security>
#   </system.webServer>
# </location>