CVE-2023-34062 - Critical Directory Traversal Vulnerability in Reactor Netty HTTP Server

Recently, a critical vulnerability identified as CVE-2023-34062 has been discovered in Reactor Netty HTTP Server, affecting versions 1.1.x prior to 1.1.13 and versions 1..x prior to 1..39. The vulnerability allows for a potential directory traversal attack, which could result in unauthorized access to sensitive files and data on the server.

This vulnerability specifically targets applications that use Reactor Netty HTTP Server configured to serve static resources. In this post, I'll break down the details of this exploit, along with a brief code snippet to help you better understand the issue. Additionally, I'll provide links to the original references and suggested steps to mitigate this vulnerability.

Exploit Details

A directory traversal attack is a type of exploit where an attacker aims to access files and directories on a server that are stored outside the web root folder. This type of access could result in the disclosure of sensitive information, ultimately compromising the security of the server.

In the case of CVE-2023-34062, the vulnerability arises when a malicious user sends a specially crafted URL to the server, which allows the attacker to potentially manipulate the application into serving files outside of the intended directory.

Here's a code snippet demonstrating a possible scenario of this attack

// Sample Reactor Netty HTTP Server configured to serve static resources
public class VulnerableServer {
    public static void main(String[] args) {
        HttpServer.create()
                .route(routes ->
                        routes.get("/static/{resource}", (request, response) -> {
                            String resource = request.param("resource");
                            // Process resource request
                        })
                )
                .bindNow();
    }
}

With this configuration, an attacker could send a request like the following example

GET /static/../../../../../../etc/passwd

This request attempts to access the /etc/passwd file, which is a sensitive file containing user account information on Unix-based systems. If the attacker were successful, the server could potentially serve the requested file, compromising the security of the application.

For more information on CVE-2023-34062 and its impact, check out the following links

1. Official CVE details: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-34062
2. Reactor Netty GitHub Repository: https://github.com/reactor/reactor-netty
3. Reactor Netty Changelog: https://github.com/reactor/reactor-netty/blob/main/CHANGELOG.md

Mitigation Steps

To mitigate this vulnerability, it's essential to update your Reactor Netty HTTP Server to a version that addresses this issue. Specifically, you should update to version 1.1.13 or 1..39, depending on the version series you're using.

If you're using version 1.1.x, update to version 1.1.13

<dependency>
    <groupId>io.projectreactor.netty</groupId>
    <artifactId>reactor-netty-http</artifactId>
    <version>1.1.13</version>
</dependency>

Or, if you're using version 1..x, update to version 1..39

<dependency>
    <groupId>io.projectreactor.netty</groupId>
    <artifactId>reactor-netty-http</artifactId>
    <version>1..39</version>
</dependency>

Additionally, consider carefully validating and sanitizing any user input related to file or resource access within your application. This step can help reduce the risk of further vulnerabilities.

Conclusion

Keeping your applications secure is a crucial aspect of software development. By addressing the CVE-2023-34062 vulnerability and ensuring your Reactor Netty HTTP Server is updated, you can protect your applications from potential directory traversal attacks. Always stay informed of the latest security vulnerabilities and updates, and take the necessary steps to maintain the safety of your applications and users.

Timeline

Published on: 11/15/2023 10:15:07 UTC
Last modified on: 11/21/2023 20:11:45 UTC