Spring4shell on Vercel

Spring4shell (CVE-2022-22965) exploits a zero-day vulnerability in Spring Framework versions before 5.3.18, 5.2.20, and 5.1.6. The vulnerability allows unauthenticated remote code execution through a malicious Content-Type header that triggers Java deserialization.

In Vercel deployments, Spring4shell manifests through several specific attack patterns:

• Deserialization of malicious objects via Content-Type: application/x-java-serialized-object headers
• JNDI injection through LDAP/RMI endpoints exposed in Spring Boot Actuator
• Prototype gadget chain exploitation via Class.forName() calls in Spring's bean factory
• Class loader manipulation through java.lang.ProcessBuilder gadget chains

Vercel-specific attack vectors include:

POST /actuator/env HTTP/1.1
Host: your-app.vercel.app
Content-Type: application/x-java-serialized-object
Content-Length: 1024

<malicious serialized payload>

The Vercel platform's default Spring Boot configurations often include Actuator endpoints (/actuator/health, /actuator/env, /actuator/beans) which, when combined with vulnerable Spring versions, create a perfect attack surface. The platform's auto-scaling can also make exploitation more reliable by providing multiple instances to target.

Detecting Spring4shell in Vercel deployments requires both automated scanning and manual verification. The middleBrick API security scanner can identify this vulnerability through several specific checks:

middleBrick Detection Capabilities:

$ middlebrick scan https://your-app.vercel.app

Security Score: C (67/100)
Critical Findings:
✓ Spring4shell (CVE-2022-22965) - Vulnerable Spring version detected
✓ Actuator endpoints exposed without authentication
✓ Java deserialization endpoints accessible
✓ Prototype gadget chain vulnerability

Manual detection methods for Vercel-specific Spring4shell:

• Version fingerprinting: Check /actuator/info for Spring Boot version
• Endpoint enumeration: Test for exposed Actuator endpoints
• Content-Type testing: Send malicious application/x-java-serialized-object headers
• JNDI endpoint discovery: Look for LDAP/RMI references in error messages

Critical Vercel-specific indicators:

$ curl -H "Content-Type: application/x-java-serialized-object" \
  https://your-app.vercel.app/actuator/env

# Look for:
- Java stack traces in responses
- Class loading error messages
- Serialized object processing logs
- JNDI reference resolution attempts

middleBrick's LLM security checks also scan for AI-related attack surfaces that might be exposed alongside Spring4shell vulnerabilities, providing comprehensive coverage of modern Vercel deployments.

Remediating Spring4shell in Vercel deployments requires both immediate patching and Vercel-specific configuration changes. Here's a comprehensive remediation strategy:

1. Immediate Patching:

// pom.xml or build.gradle
<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-parent</artifactId>
  <version>2.7.14</version> <!-- Patched version -->
</dependency>

2. Vercel Configuration:

// vercel.json - Security hardening
{
  "headers": [
    {
      "source": "(.*)",
      "headers": [
        "Content-Security-Policy: default-src 'self'"
      ]
    }
  ],
  "rewrites": [
    {
      "source": "/actuator/(.*)",
      "destination": "/403"
    }
  ]
}

3. Spring Boot Security Configuration:

// src/main/resources/application.properties
# Disable vulnerable endpoints
management.endpoints.web.exposure.include=health,info
management.endpoint.env.enabled=false
management.endpoint.beans.enabled=false

# Disable deserialization
spring.autoconfigure.exclude=org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration

# Security headers
server.servlet.context-path=/api
server.use-forward-headers=true

4. Vercel Build Hook Security:

// package.json
{
  "scripts": {
    "vercel-build": "mvn clean package -DskipTests -Dspring.profiles.active=vercel"
  }
}

5. Runtime Protection:

// src/main/java/com/example/security/SecurityConfig.java
@Configuration
public class SecurityConfig {
    @Bean
    public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
        http.csrf(csrf -> csrf.disable())
 authz
                .requestMatchers("/actuator/**").denyAll()
                .requestMatchers("/api/**").authenticated()
                .anyRequest().permitAll()
 headers
                .contentTypeOptions(Customizer.withDefaults())
}

6. Monitoring and Alerting:

// Add to vercel.json for security monitoring
{
  "build": {
    "env": {
      "SPRING_SECURITY_CHECKS": "enabled",
      "ACTUATOR_SECURITY": "disabled"
    }
  },
  "functions": {
    "api/**/*.js": {
      "runtime": "nodejs18.x",
      "maxDuration": 30
    }
 }
}

After implementing these remediations, use middleBrick to verify the fixes:

$ middlebrick scan --retest https://your-app.vercel.app

Security Score: A (92/100)
✓ Spring4shell vulnerability resolved
✓ Actuator endpoints secured
✓ Deserialization blocked
✓ Security headers implemented