External risk intelligence

MCMS ueditor Arbitrary File Upload leads to Code Execution

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2025-29287

MCMS is a content management system. Such applications are commonly deployed as internet-facing web portals to manage and serve public content, making the file upload functionality typically accessible via the web interface.

Unrestricted File Upload

Mingsoft Mcms

5.4.3

Halo Surface Signal: 4 out of 5 — likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A security vulnerability has been identified in the ueditor component of MCMS, specifically affecting version 5.4.3. This issue allows for arbitrary code execution through the upload of specially crafted files, presenting a significant risk to systems utilizing this technology. The nature of this vulnerability requires immediate attention to confirm relevance and potential exposure within our environment.

Unrestricted file uploads allow attackers to run code.
Content management systems are often internet-facing.
Assess MCMS for exposure and potential impact.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by uploading a specially crafted file through the ueditor component of MCMS. This bypasses normal file restrictions, allowing for the execution of arbitrary code on the server.

No authentication required for access.
Upload a crafted file through ueditor.
Arbitrary code execution.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could allow an unauthenticated attacker to upload arbitrary files to the MCMS system. When supported by the advisory, this could lead to the execution of malicious code, potentially impacting the integrity and availability of the system.

Arbitrary code execution on the system.
Uploading a crafted file via a network.
System compromise and data manipulation.

Operational Fix

Recommended remediation, mitigation, and detection steps

Identifying the appropriate teams to address this vulnerability requires understanding the deployment of MCMS. Typically, application owners or platform teams would be responsible for managing the MCMS instance. The first practical step is to locate all MCMS deployments, determine their exposure and criticality, identify the accountable owner for each instance, and then plan remediation based on these findings.

Application or platform teams own the issue.
Verify MCMS deployment and reachability.
Plan remediation based on identified risk.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is MCMS and what is the ueditor component?

MCMS is a content management system developed by Mingsoft, commonly used to build and manage website content. The ueditor component is an integrated rich text editor within the platform that allows users to create and format content. This feature often includes functions for handling file attachments or media uploads, which is where this specific vulnerability resides.

What does CWE-434 mean regarding CVE-2025-29287?

CWE-434 refers to an Unrestricted Upload of File with Dangerous Type. In the context of CVE-2025-29287, it means the application does not sufficiently validate or restrict the files being uploaded through the editor. Because the system accepts these files without proper checks, an attacker can upload a malicious script, which the server may then execute as code.

How does an attacker trigger this file upload vulnerability?

An attacker triggers this by interacting with the ueditor component over the network to upload a crafted file containing malicious code. No authentication or login is required to reach this function. Simply attempting to upload a standard, benign file or accessing parts of the site that do not utilize the ueditor component for file handling will not trigger this specific vulnerability.

Is my instance of MCMS at risk if it is internal?

According to Halo Surface Signal, MCMS instances are typically designed as internet-facing portals to serve public content, which increases the likelihood of external reachability. However, even if your instance is currently internal, it remains susceptible if it is reachable by any user or compromised machine on your private network. You should verify the network path to your deployment to determine its true reachability.

What should I do if I am running MCMS v5.4.3?

Your first step is to locate all instances of MCMS within your environment to understand your footprint. Once identified, determine which teams own these specific deployments. You should then assess the reachability of each instance to prioritize your response, as public-facing sites face higher risk. Work with the responsible application or platform teams to plan for remediation and apply necessary updates.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.