CVE-2023-20883: Denial-of-Service Attack in Spring Boot with Spring MVC and Reverse Proxy Cache - A Detailed Analysis

A recently discovered vulnerability (CVE-2023-20883) affects multiple versions of the popular Spring Boot framework, particularly when using Spring MVC in combination with a reverse proxy cache. In this post, we will explore the details of this vulnerability, discussing the affected versions, the root cause of the issue, and the potential consequences of an exploit. Furthermore, we will provide code snippets illustrating the problem and the mitigation techniques, as well as links to the original references.

Older unsupported versions

It is crucial to note that the vulnerability is present only when Spring MVC is used in conjunction with a reverse proxy cache.

Root Cause

The issue arises due to a lack of proper cache handling, specifically when using Spring MVC together with a reverse proxy cache. When certain conditions are met, the application becomes vulnerable to a denial-of-service (DoS) attack.

Exploit Details

An attacker can exploit this vulnerability to execute a DoS attack against the target application, causing it to crash or become unresponsive. This can lead to service disruptions and business impact.

Code Snippet

The following code snippet shows a typical Spring MVC configuration that may be vulnerable to this issue:

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.web.servlet.config.annotation.CorsRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@SpringBootApplication
public class VulnerableSpringBootApp {

    public static void main(String[] args) {
        SpringApplication.run(VulnerableSpringBootApp.class, args);
    }

    @Bean
    public WebMvcConfigurer corsConfigurer() {
        return new WebMvcConfigurer() {
            @Override
            public void addCorsMappings(CorsRegistry registry) {
                registry.addMapping("/**")
                        .allowedOrigins("*")
                        .allowedMethods("*")
                        .allowedHeaders("*")
                        .allowCredentials(true).maxAge(360);
            }
        };
    }
}

Here are the links to the original references for further information and the official patch

- Spring Boot Security Advisory
- CVE-2023-20883 - National Vulnerability Database

Conclusion

The CVE-2023-20883 vulnerability poses a significant risk to applications using Spring Boot with Spring MVC and a reverse proxy cache. It is essential for developers and administrators to upgrade their applications to a non-vulnerable version of Spring Boot as soon as possible, while also assessing their existing configurations to ensure they are not susceptible to this issue. By doing so, they can mitigate potential denial-of-service attacks and protect their applications from this security risk.

Timeline

Published on: 05/26/2023 17:15:00 UTC
Last modified on: 06/08/2023 14:40:00 UTC