CVE-2025-4260: Zhangyanbo2007 Youkefu RCE Vulnerability

CVE-2025-4260 Overview

CVE-2025-4260 is an insecure deserialization vulnerability affecting zhangyanbo2007 youkefu through version 4.2.0. The flaw resides in the impsave function of m\web\handler\admin\system\TemplateController.java. Manipulation of the dataFile argument triggers untrusted data deserialization, which an authenticated remote attacker can abuse over the network. The exploit details have been disclosed publicly, increasing the likelihood of opportunistic attempts against exposed instances. The weakness is categorized under [CWE-20] (Improper Input Validation) and currently carries no vendor patch reference in public advisories.

Critical Impact
Authenticated remote attackers can submit crafted serialized data to the impsave endpoint to influence application state, potentially enabling object injection within the youkefu administration interface.

Affected Products

zhangyanbo2007 youkefu 4.2.0
zhangyanbo2007 youkefu prior 4.2.0 releases
Deployments exposing the admin TemplateController endpoint

Discovery Timeline

2025-05-05 - CVE-2025-4260 published to NVD
2025-10-10 - Last updated in NVD database

Technical Details for CVE-2025-4260

Vulnerability Analysis

The vulnerability resides in the impsave handler within TemplateController.java, part of the youkefu administrative web module. The endpoint accepts a dataFile parameter and processes it through a Java deserialization routine without sufficient validation of the incoming object stream. Untrusted input flowing into ObjectInputStream.readObject() style logic enables an attacker to influence which classes get instantiated during reconstruction. The attack requires low privileges and no user interaction, and it is reachable over the network through the admin interface.

Root Cause

The root cause is improper input validation [CWE-20] on the dataFile argument before deserialization. The handler trusts data supplied by an authenticated user and reconstructs Java objects without enforcing class allowlists, type checks, or integrity verification. This pattern lets attackers leverage gadget chains present on the application classpath.

Attack Vector

An authenticated attacker sends a crafted HTTP request to the impsave route with a malicious serialized payload in the dataFile parameter. When the controller deserializes the payload, it instantiates attacker-chosen objects. Depending on the libraries available in the youkefu deployment, this can lead to logic abuse, state tampering, or chained code execution through known Java gadget chains.

No verified exploit code is published in the NVD references. See the GitHub Vulnerability Document and VulDB entry #307364 for the public technical disclosure.

Detection Methods for CVE-2025-4260

Indicators of Compromise

HTTP POST requests to admin paths invoking impsave with binary or Base64-encoded dataFile parameter values.
Java stack traces in application logs referencing ObjectInputStream, readObject, or TemplateController.impsave.
Unexpected child processes spawned by the youkefu Java application user following admin template import activity.

Detection Strategies

Inspect web server access logs for requests targeting the youkefu template import endpoint, particularly from accounts that do not typically perform administrative tasks.
Apply Web Application Firewall (WAF) rules that flag serialized Java magic bytes (AC ED 00 05) or the Base64 prefix rO0AB in request bodies.
Correlate admin session activity with subsequent process creation events on the host running the youkefu service.

Monitoring Recommendations

Forward youkefu application and servlet container logs to a centralized analytics platform and alert on deserialization exceptions.
Monitor outbound connections from the youkefu host for anomalous destinations that may indicate gadget-chain triggered callbacks.
Track authentication events for the admin interface and alert on access from new geographies or user agents.

How to Mitigate CVE-2025-4260

Immediate Actions Required

Restrict network access to the youkefu admin interface using firewall rules, VPN gating, or reverse-proxy allowlists.
Rotate administrative credentials and review account inventories to remove unused or shared admin users.
Audit recent template import activity for unrecognized dataFile submissions and remove any suspicious uploaded artifacts.

Patch Information

No official vendor patch is referenced in NVD or VulDB at the time of publication. Track the upstream repository and the VulDB advisory #307364 for fix availability. Until a patched release is published, treat youkefu 4.2.0 and earlier as vulnerable.

Workarounds

Disable or block the impsave route at the reverse proxy if template import functionality is not required.
Enforce strict authentication and multi-factor authentication on all admin accounts that can reach the vulnerable endpoint.
Run the youkefu Java process under a least-privilege service account with no shell access and restricted file system permissions.
Deploy a Java Agent or JVM configuration that enforces a deserialization allowlist for the application classpath.

bash

# Example reverse-proxy block for the vulnerable endpoint (nginx)
location ~* /admin/.*/impsave {
    deny all;
    return 403;
}