CVE-2025-4258: Zhangyanbo2007 Youkefu RCE Vulnerability

CVE-2025-4258 Overview

CVE-2025-4258 is an unrestricted file upload vulnerability in zhangyanbo2007 youkefu through version 4.2.0. The flaw resides in the Upload function of \youkefu-master\src\main\java\com\ukefu\webim\web\handler\resource\MediaController.java. Attackers manipulate the imgFile argument to upload arbitrary files to the server. The issue is remotely exploitable and a public proof-of-concept has been disclosed. The weakness maps to [CWE-284] Improper Access Control. Authenticated users with low privileges can leverage the missing upload restrictions to place attacker-controlled content on the host, including content that may lead to follow-on code execution depending on server configuration.

Critical Impact
Remote authenticated attackers can upload arbitrary files through the imgFile parameter, enabling potential webshell placement and further compromise of the youkefu web instance.

Affected Products

zhangyanbo2007 youkefu versions up to and including 4.2.0
Component: MediaController.java in youkefu-master\src\main\java\com\ukefu\webim\web\handler\resource\
Function: Upload accepting the imgFile parameter

Discovery Timeline

2025-05-05 - CVE-2025-4258 published to NVD
2025-10-10 - Last updated in NVD database

Technical Details for CVE-2025-4258

Vulnerability Analysis

The vulnerability exists in the Upload handler of the MediaController class within the youkefu webim resource handler package. The endpoint processes the imgFile request parameter without enforcing restrictions on file type, extension, content, or destination path. An attacker submitting a crafted multipart request can place arbitrary files into a server-accessible directory. Because youkefu is a Java-based web application, uploaded content placed within served directories can become executable resources depending on deployment. The flaw is network-reachable and requires low privileges, with no user interaction needed to trigger the upload path.

Root Cause

The root cause is missing access control and missing validation on the imgFile upload parameter inside MediaController.java. The handler accepts the file stream and writes it to disk without confirming the MIME type, extension allowlist, content magic bytes, or safe storage location. This omission classifies the defect as [CWE-284] Improper Access Control combined with classic unrestricted upload behavior.

Attack Vector

An attacker with valid low-privilege credentials sends an HTTP POST request to the media upload endpoint exposed by MediaController. The request includes a multipart imgFile field carrying attacker-chosen content, such as a server-side script masquerading as an image. The application persists the file to the resource directory. If that directory is served by the application container, the attacker requests the uploaded path to trigger execution or to host malicious content. Public proof-of-concept documentation is available in the GitHub PoC Documentation referenced by VulDB.

No verified exploit code is reproduced here. Refer to the VulDB CTI ID #307362 entry and the public PoC for technical reproduction details.

Detection Methods for CVE-2025-4258

Indicators of Compromise

Unexpected files with executable extensions such as .jsp, .jspx, or .war in youkefu media or resource upload directories.
HTTP POST requests to the youkefu MediaController upload endpoint containing an imgFile field with non-image content types.
New files in upload directories owned by the application service account with modification times outside change windows.
Outbound connections initiated by the youkefu Java process to unfamiliar IPs shortly after file upload activity.

Detection Strategies

Inspect web server and application logs for repeated POSTs to the MediaController upload route from a single authenticated session.
Hash and inventory files in youkefu upload directories, then alert when non-image MIME content lands in image storage paths.
Deploy a web application firewall rule that validates Content-Type and file magic bytes for the imgFile multipart field.

Monitoring Recommendations

Monitor process creation events spawned by the youkefu Java runtime, especially shell or scripting interpreters launched from upload directories.
Track filesystem writes to youkefu resource paths and correlate with HTTP request identifiers in application logs.
Alert on authentication anomalies for youkefu accounts that subsequently call media upload endpoints in rapid succession.

How to Mitigate CVE-2025-4258

Immediate Actions Required

Restrict network access to the youkefu administrative and media upload endpoints to trusted networks until a vendor fix is applied.
Review existing files in youkefu upload directories and remove any non-image artifacts.
Rotate credentials for any youkefu accounts that may have been used to test or exploit the upload endpoint.
Disable the media upload feature at the reverse proxy layer if it is not required for business operations.

Patch Information

No vendor patch or fixed release has been published in the references available for CVE-2025-4258. Track the project repository for zhangyanbo2007/youkefu and the VulDB entry #307362 for remediation updates. Until a patched build is released, treat all instances running version 4.2.0 and earlier as vulnerable.

Workarounds

Place a reverse proxy or WAF rule in front of youkefu that enforces an allowlist of image MIME types and rejects multipart requests carrying script content in the imgFile field.
Configure the application container so that the upload destination directory is not interpreted or executed as server-side code.
Apply filesystem-level restrictions that prevent the youkefu service account from writing files with executable extensions to web-served paths.
Require multi-factor authentication for accounts that can reach the media upload endpoint to raise the cost of low-privilege abuse.

bash

# Example nginx rule rejecting non-image content on the youkefu upload endpoint
location /resource/image/upload {
    if ($content_type !~* "^(multipart/form-data).*") { return 403; }
    client_max_body_size 5m;
    proxy_pass http://youkefu_backend;
}