Exposing a Major Security Flaw in MailDev: Inside the CVE-2024-27448 Vulnerability

April 4 - Vulnerability Tim Author

MailDev, a widely-used mail server application, has recently come under scrutiny due to a significant security flaw within its codebase. This vulnerability, designated as CVE-2024-27448, poses a serious risk to server integrity and data security. In this blog, we delve into what makes this vulnerability a critical issue, particularly for enterprises and developers relying on MailDev for email testing and development.

MailDev at a Glance:

MailDev is an essential tool for developers, providing an easy-to-use platform for testing emails during development. It serves a broad user base, including small to large enterprises, making the impact of this vulnerability potentially vast.

Latest Affected Version:

Version Affected: 2.1.0

Tested Vulnerable Versions: 2.x.x

Understanding the Vulnerability:

At the core of this vulnerability is the saveAttachment function within maildev/lib/mailserver.js. This function’s primary role is to save email attachments. However, a critical oversight is the lack of proper path sanitization, leaving it open to path traversal attacks.

Technical Insight

Path traversal attacks allow attackers to access directories and files stored outside the web root folder. If an attacker can manipulate variables that reference files, they can potentially access sensitive files and data.

Figure 1 – Vulnerable Function

The Consequences of Exploitation:

While discussing the specifics of an exploit poses ethical concerns, it’s vital to understand the gravity of this vulnerability. Exploiting this flaw could lead to unauthorized modification or deletion of critical files and even remote code execution.

Exploit Demo:

First we will start an instance of MailDev

Figure 2 – Starting MailDev: A visual guide to initiating a MailDev instance.

We will then run the exploit this will detect the version of MailDev running and download the corresponding version of routes.js from MailDev on GitHub. It will the inserts a backdoor into the routes.js file and upload it to the server overwriting the existing routes.js file.

Figure 3 – Running the Exploit: Steps demonstrating the detection and exploitation process

We have now successfully backdoored the web application the shell access can be accessed at /shell?cmd=

Figure 4 – Remote Code Execution: Highlighting the potential for gaining unauthorized access.


This vulnerability highlights the need for constant vigilance in software development and usage. It’s imperative for users of MailDev to update their software to the latest, patched version to mitigate this security risk.

Encouraging Action:

We urge all MailDev users to take immediate action to secure their systems. This incident serves as a reminder of the ever-evolving nature of cybersecurity threats.

To learn more about how we integrate best practice cyber security measures with business strategies to keep your IT systems secure and your data safe – get in touch with us!

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