External risk intelligence

CKEditor Redmine Plugin Unrestricted File Upload Vulnerability.

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2023-31541

The vulnerability exists in a plugin for Redmine, a web-based project management application. Redmine instances are commonly deployed as internet-facing web applications to allow distributed teams to collaborate. Since the vulnerable file upload feature is part of the standard web interface, it is commonly exposed to the network.

Unrestricted File Upload

Ckeditor

1.2.3

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 vulnerability in a file upload feature of a Redmine plugin could allow attackers to upload arbitrary files to servers. This could potentially lead to serious security compromises if the plugin is in use. The main concern is confirming if this specific plugin is deployed within our Redmine environments.

Allows unauthorized file uploads to servers.
Could impact any deployed Redmine instances.
Confirm if the plugin is used internally.

Attack Path

How an attacker could exploit the issue

An attacker can leverage this vulnerability by uploading arbitrary files to the server through the "Browse and upload images" feature of a CKEditor plugin for Redmine. This allows them to place malicious files on the server, which could lead to further compromise.

No user interaction or special privileges required.
Uploading a specially crafted file.
Remote code execution and data compromise.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could allow an attacker to upload arbitrary files to the server when the 'Browse and upload images' feature is accessible, potentially impacting the system's integrity and availability.

Arbitrary files can be uploaded to the server.
Access to the 'Browse and upload images' feature.
System compromise and service disruption.

Operational Fix

Recommended remediation, mitigation, and detection steps

Determining precise ownership requires cross-referencing the affected Redmine instances with your internal asset inventory and identifying the corresponding application or platform teams. The immediate first step is to locate all deployments of the CKEditor plugin for Redmine within your environment to understand the potential exposure and prioritize remediation efforts.

Application owners must own the issue.
Verify plugin reachability and business criticality.
Plan remediation based on identified risk.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

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Frequently asked questions

What is the CKEditor plugin for Redmine?

It is an add-on component used within Redmine, a popular web-based project management platform. This specific plugin extends Redmine's text editing capabilities, allowing users to embed and manage images directly within project tasks or documentation. Because Redmine is often used by distributed teams, this plugin is frequently integrated into collaborative environments to simplify how files and visuals are shared across project workspaces.

What does CVE-2023-31541 mean in simple terms?

This vulnerability is classified as Unrestricted File Upload (CWE-434). It means the software does not properly check the type or content of files being uploaded through its image tool. Because the system lacks these safeguards, it can be tricked into accepting malicious files instead of standard images. If successful, an attacker can store unauthorized files on the server, potentially gaining control over the system.

How can an attacker trigger this vulnerability?

An attacker exploits this by interacting with the 'Browse and upload images' feature directly. The bug does not require the attacker to have an existing account or any special permissions to function. Simply accessing the feature and submitting a specially crafted file is sufficient to bypass intended restrictions. Note that this flaw is specific to the upload process itself; it is not triggered by standard navigation or viewing existing project pages.

Is my organization at risk from this vulnerability?

Halo Surface Signal indicates a high likelihood of concern because Redmine instances are typically deployed as internet-facing web applications. Since this file upload feature is a core part of the web interface, any instance reachable over the network may be exposed to unauthorized file uploads. If your team hosts Redmine to facilitate external collaboration, your risk profile is elevated.

What should I do if I use this plugin?

Your first step is to inventory your Redmine deployments to confirm if this specific version (v1.2.3) is active. Once located, work with your application owners to evaluate the plugin's business necessity against the risk of compromise. You should restrict access to the affected feature or disable the plugin entirely until you can transition to a secure version or apply available updates provided by the vendor.

References

github.com/DreamD2v/CVE-2023-31541/blob/main/CVE-2023-31541.md

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.