A recently discovered vulnerability (CVE-2025-48734) in Apache Commons BeanUtils can allow attackers to gain elevated privileges and potentially execute arbitrary code on your Java application. This long-read will break down what caused the problem, how it can be exploited, how it was fixed, and what actions you should take. The language is kept simple and clear to make this accessible even if you’re not a Java expert.

Background: What Is Apache Commons BeanUtils?

Apache Commons BeanUtils is a popular Java library that makes it easy to work with JavaBeans—reusable software components for Java. Developers often use BeanUtils to manipulate JavaBeans properties dynamically, such as copying, retrieving, or setting property values by name.

What Happened? (The Vulnerability)

In versions of Commons BeanUtils before 1.11. (1.x) and before 2..-M2 (2.x), there is an improper access control vulnerability.

The Details

The library allows external property paths to be passed to methods like getProperty() and getNestedProperty(). If an attacker can influence these paths, they can access all properties of an object—including sensitive and special ones not usually meant to be accessible.

A key point here is the "declaredClass" property on Java enum objects. This property leads to the ClassLoader, and if an attacker can interact with it, they could potentially use it for more dangerous activities, including remote code execution.

What about BeanIntrospector?

In earlier versions, a BeanIntrospector class could protect against this by removing or suppressing the declaredClass property. However, this protection was not enabled by default.

The Attack Path

Suppose your application lets the user specify property paths, possibly via HTTP parameters. You call:

String propertyValue = beanUtilsBean.getProperty(enumObject, userSuppliedProperty);

If userSuppliedProperty is set to "declaredClass", it gives access to the enum’s class, including its ClassLoader. An attacker might chain this access with other vulnerabilities to load arbitrary classes or run malicious code.

Code Snippet: The Vulnerable Pattern

import org.apache.commons.beanutils.BeanUtilsBean;

// Assume enumObject is controlled or known
String value = BeanUtilsBean.getInstance().getProperty(enumObject, "declaredClass");
System.out.println(value); // This exposes the class loader

If enumObject is an Enum, "declaredClass" gives access to internal Java class mechanisms.

Version 2..-M2 (2.x)

These versions added a special BeanIntrospector that _suppresses the "declaredClass" property by default_. Now, you can’t access that property unless you specifically disable the new protection (which you should not do).

Here’s how BeanIntrospector blocks access (simplified)

// In the new, fixed versions
BeanUtilsBean beanUtils = BeanUtilsBean.getInstance();
// Now, this will NOT expose the class or classloader
String value = beanUtils.getProperty(enumObject, "declaredClass"); // Throws exception

Users of org.apache.commons:commons-beanutils2 (2.x) before 2..-M2

If your project depends on either artifact in a vulnerable version, you are exposed.

Update your Maven pom.xml or build file as shown

<!-- For 1.x users -->
<dependency>
    <groupId>commons-beanutils</groupId>
    <artifactId>commons-beanutils</artifactId>
    <version>1.11.</version>
</dependency>

<!-- For 2.x users -->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-beanutils2</artifactId>
    <version>2..-M2</version>
</dependency>

References

- Apache Commons BeanUtils Project
- Security Fix Announcement
- GitHub Security Advisory
- Upgrading Guide Section 2.5

Summary Table

| Release | Fixed Version | Affected? |
|---------------------|------------------|---------------------|
| 1.x (Beanutils) | 1.11. | < 1.11.: YES |
| 2.x (Beanutils2) | 2..-M2 | < 2..-M2: YES |

Why This Matters

Vulnerabilities like CVE-2025-48734 are dangerously subtle. Allowing external input to access internal properties can have catastrophic consequences, especially in enterprise applications where Java class loaders control what code runs. Always keep your dependencies up to date and follow secure coding best practices.


Protect your applications by upgrading today. If you have questions, check out the official Apache Commons BeanUtils security guidance.


*Written exclusively for you by an AI assistant tuned to simple, direct technical language.*

Timeline

Published on: 05/28/2025 14:15:34 UTC
Last modified on: 05/28/2025 18:15:27 UTC