A newly published vulnerability, CVE-2025-46392, affects the popular Apache Commons Configuration 1.x library. This vulnerability exposes systems to risks of Denial of Service (DoS) and potential server failures through uncontrolled resource consumption when processing untrusted, or malicious, configuration files.

This post will break down what this vulnerability means, why it happens, how it can be exploited, and what you should do to protect your applications.

What Is Apache Commons Configuration?

Apache Commons Configuration is a Java library that helps developers load and manage configuration data from various file formats (XML, properties files, INI files, etc.). It's widely used in Java projects for its flexibility and ease of use.

Description of the Vulnerability

CVE-2025-46392 refers to a set of issues in version 1.x of the Apache Commons Configuration library, where uncontrolled resource consumption can happen if the library processes configs crafted by an attacker.

Key points

- If your application allows users to upload or modify configuration files, an attacker could craft a file that causes the library to consume huge amounts of memory or CPU.
- If your code loads configuration data from untrusted sources (such as files uploaded by users, remote endpoints, or any unknown/untrusted input), your system is at risk.
- The Apache team has no plans to patch version 1.x, only the newer 2.x versions address these weaknesses.

How Does the Vulnerability Work?

The core problem is that the code in version 1.x does not implement controls on how much data can be loaded, stored, or processed at once. Certain methods or configuration file types can cause the library to allocate huge data structures or perform time-consuming computations.

Suppose you have code like this

import org.apache.commons.configuration.Configuration;
import org.apache.commons.configuration.PropertiesConfiguration;
import java.io.File;

public class ConfigLoader {
    public static void main(String[] args) throws Exception {
        Configuration config = new PropertiesConfiguration(new File("config.properties"));
        // Work with the config...
    }
}

If config.properties is controlled by an attacker, it could, for example, contain millions of very large or deeply-nested properties. There's no internal limit-checking in the code to stop this, so you may hit out-of-memory or excessive resource usage.

- An attacker uploads a config.properties file like the one below

# Example of resource exhaustion via large value
key1=aaaaaaaaaaaa...[10MB of 'a's]
key2=bbbbbbbbbbbb...[another 10MB of b's]
# Repeat for thousands of keys

Or,

# Adding thousands or millions of unnecessary keys
key1=value1
key2=value2
# up to millions of keys

The attacker’s purpose: force the server to allocate excessive memory or spend a long time reading/parsing these files, which may result in:

1. Prefer Apache Commons Configuration 2.x

The issues have been fixed in version 2.x (official migration guide).

- The new version uses a separate Maven groupId and package namespace, so you can migrate parts of your codebase without conflicts.

Sample Maven snippet

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-configuration2</artifactId>
    <version>2.x.x</version>
</dependency>

2. Restrict User Control

Never allow users or untrusted parties to directly upload or supply configuration files unless those files are fully content-validated and size-limited *before* being parsed by the library.

Maximum file size (e.g., <1MB)

- Max number of keys/lines checked prior to loading

4. Monitor and Alert

Watch for sudden spikes in resource consumption, indicating a possible exploit.

Apache Security Advisory:

CVE-2025-46392 Details (Official Mailing List)
- Commons Configuration 2.x Documentation
- Upgrade Guide 1.x to 2.x

Conclusion

CVE-2025-46392 is a real danger for anyone using Apache Commons Configuration 1.x with untrusted configuration sources. You should take this warning seriously, review all usage of this library in your applications, and plan your migration to the secured 2.x version as soon as possible.

Put limits in place wherever you must use version 1.x

Stay safe and check for further advisories from the Apache team for updates.


> _If you need practical help migrating from version 1.x to 2.x, or want to test if your application is vulnerable, consider reaching out to a security specialist or your internal security team._

Timeline

Published on: 05/09/2025 10:15:17 UTC
Last modified on: 05/13/2025 20:15:30 UTC