CVE-2025-9400: Wanglongcn Yifang CMS RCE Vulnerability

CVE-2025-9400 Overview

CVE-2025-9400 is an unrestricted file upload vulnerability affecting YiFang CMS versions up to 2.0.5. The flaw resides in the mergeMultipartUpload function within app/utils/base/plugin/P_file.php. Attackers can manipulate the File argument to upload arbitrary files to the server. Exploitation requires network access and low-level authentication, with no user interaction. The vendor, wanglongcn, was contacted prior to public disclosure but did not respond. A public proof-of-concept has been published, increasing the risk of opportunistic exploitation against exposed instances. The weakness is classified under [CWE-284] Improper Access Control.

Critical Impact
Authenticated remote attackers can upload arbitrary files through the multipart upload merge function, enabling potential web shell deployment and content tampering on affected YiFang CMS instances.

Affected Products

YiFang CMS versions up to and including 2.0.5
wanglongcn yifang (all versions through 2.0.5)
Deployments using app/utils/base/plugin/P_file.php with the mergeMultipartUpload function

Discovery Timeline

2025-08-25 - CVE-2025-9400 published to NVD
2026-04-29 - Last updated in NVD database

Technical Details for CVE-2025-9400

Vulnerability Analysis

The vulnerability exists in the mergeMultipartUpload function inside app/utils/base/plugin/P_file.php. This function handles the server-side merging of multipart file uploads in YiFang CMS. The File argument is processed without sufficient validation of file type, extension, or destination path. An authenticated attacker can submit crafted upload requests that bypass intended restrictions on uploaded content.

Because the upload routine does not enforce a strict allowlist of acceptable file types, attackers can place executable scripts within web-accessible directories. The vulnerability falls under [CWE-284] Improper Access Control, reflecting the absence of adequate authorization or validation checks on the upload merge operation. Public exploit material is available through the referenced GitHub PoC Documentation.

Root Cause

The root cause is missing validation logic in the mergeMultipartUpload function. The function trusts client-supplied parameters when assembling and persisting the merged file. There is no enforcement of file type restrictions, MIME validation, or destination path sanitization before writing data to disk.

Attack Vector

Exploitation occurs over the network against any reachable YiFang CMS instance. The attacker must hold low-level credentials to invoke the upload endpoint. Once authenticated, the attacker initiates a multipart upload and supplies a manipulated File argument during the merge step. The malicious payload is written to a location accessible by the web server. Technical analysis details are available in the VulDB #321236 Details entry.

Detection Methods for CVE-2025-9400

Indicators of Compromise

Unexpected files with executable extensions such as .php, .phtml, or .phar appearing in YiFang CMS upload directories
HTTP requests targeting endpoints that invoke mergeMultipartUpload with unusual File parameter values
Web server processes spawning shell or scripting interpreters shortly after upload activity
Outbound network connections from the web server to attacker-controlled infrastructure following file upload events

Detection Strategies

Review web server access logs for POST requests to multipart upload merge endpoints originating from a single low-privilege account
Monitor file integrity in YiFang CMS upload and plugin directories for new or modified files
Inspect app/utils/base/plugin/P_file.php invocation patterns for anomalous parameter content
Correlate authentication events with subsequent file creation to identify abuse of valid accounts

Monitoring Recommendations

Enable verbose logging on the YiFang CMS application and forward logs to a centralized analytics platform
Alert on web shell signatures and suspicious PHP files written within document roots
Track process execution lineage from the PHP interpreter to identify post-upload command activity
Baseline expected upload behavior per user and flag deviations in file count, size, or extension

How to Mitigate CVE-2025-9400

Immediate Actions Required

Restrict network exposure of YiFang CMS administrative and upload endpoints to trusted networks only
Audit existing accounts and rotate credentials for any users with upload privileges
Inspect upload directories for unauthorized files and remove any unrecognized scripts
Disable or remove the affected upload functionality if it is not required for business operations

Patch Information

As of the last NVD update on 2026-04-29, the vendor wanglongcn has not issued a public patch or advisory. The original reporter confirmed that the vendor did not respond to disclosure outreach. Administrators should monitor the project repository for future updates and consider migrating to an actively maintained CMS if no fix is released. Refer to the VulDB #321236 Incident Report for the latest disclosure status.

Workarounds

Place YiFang CMS behind a web application firewall configured to block uploads of executable file types
Configure the web server to deny execution of scripts within upload directories using filesystem-level restrictions
Enforce strict file extension and MIME type allowlists at a reverse proxy layer
Remove write or execute permissions from upload paths wherever feasible

bash

# Example nginx configuration to prevent script execution in upload directories
location ^~ /uploads/ {
    location ~* \.(php|phtml|phar|pl|py|jsp|asp|sh|cgi)$ {
        deny all;
        return 403;
    }
}