Cors Wildcard in Spring Boot with Dynamodb

A CORS wildcard in Spring Boot (allowedOrigins = "*") combined with DynamoDB as a backend data store can unintentionally expose your data and broaden the impact of misconfigured authorization. When your frontend is served from any origin while your backend calls DynamoDB, a reflected or stored cross-origin request can carry authenticated cookies or bearer tokens, causing the browser to include credentials on cross-origin requests. If authorization decisions rely solely on the origin header or are missing at the DynamoDB data-access layer, this setup can enable unauthorized account or data access across origins.

In a typical Spring Boot service, a controller method might call DynamoDB to retrieve or update a user resource. If CORS permits all origins and the endpoint does not validate the request source or enforce ownership checks on the retrieved DynamoDB item, an attacker can craft a request from a malicious site that leverages the victim’s credentials. For example, an endpoint like /users/{userId} that queries DynamoDB for the item with the provided ID could be invoked cross-origin if the user is authenticated, returning data that should be restricted. Because DynamoDB does not enforce browser-origin policies, the backend must implement strict authorization and avoid reflecting permissive CORS rules that imply trust at the network boundary.

The risk is compounded when the Spring Boot application uses AWS credentials or temporary tokens that are not scoped per request or per user. An attacker who can inject a cross-origin request may leverage the permissions associated with the compromised credentials to issue low-level DynamoDB operations, such as GetItem or Query, against tables that contain sensitive records. While CORS is a browser-enforced mechanism, it interacts with backend logic; permissive CORS settings can mask missing ownership checks in the DynamoDB access code and make it easier to chain vulnerabilities like Broken Object Level Authorization (BOLA).

Spring Boot’s default configuration with a wildcard CORS policy does not automatically protect you from these concerns. Developers must explicitly ensure that CORS rules align with the principle of least privilege, validating not only origins but also HTTP methods and headers. Authorization checks must be tied to each DynamoDB operation, confirming that the requesting user has the right to access the specific item or table. Without these controls, the convenience of a wildcard origin can expose DynamoDB-backed endpoints to unauthorized reads or writes via cross-origin abuse.

To detect such issues, scanning tools can analyze your Spring Boot configuration and runtime behavior, flagging permissive CORS origins alongside DynamoDB access patterns that lack user-level authorization. They may also verify that credentials are not unnecessarily exposed to browser contexts and that data exposure findings related to cross-origin data leakage are surfaced. This helps teams understand how permissive settings interact with backend data stores and prioritize fixes that tighten both CORS and DynamoDB authorization.

Remediation starts with tightening CORS in your Spring Boot application. Instead of using a wildcard, specify exact origins that your frontend serves from. Combine this with explicit authentication checks before any DynamoDB call, and enforce ownership at the item level. Below are focused code examples that demonstrate how to secure a Spring Boot service that interacts with DynamoDB.

First, configure CORS to allow only trusted origins and ensure credentials are not automatically exposed to untrusted sites. In your configuration class, define a bean that restricts origins and methods:

@Configuration
public class CorsConfig implements WebMvcConfigurer {

    @Bean
    public WebMvcConfigurer corsConfigurer() {
        return new WebMvcConfigurer() {
            @Override
            public void addCorsMappings(CorsRegistry registry) {
                registry.addMapping("/api/**")
                        .allowedOrigins("https://app.yourcompany.com", "https://staging.yourcompany.com")
                        .allowedMethods("GET", "POST", "PUT", "DELETE")
                        .allowedHeaders("Content-Type", "Authorization")
                        .exposedHeaders("X-Request-ID")
                        .maxAge(3600)
                        .allowCredentials(false); // avoid true unless necessary
            }
        };
    }
}

Next, secure DynamoDB access in your service layer by validating the authenticated user against the item’s ownership. Use the AWS SDK for Java v2 and inject the authenticated user’s identity (for example from Spring Security) into each DynamoDB request:

@Service
public class UserProfileService {

    private final DynamoDbEnhancedClient enhancedClient;
    private final UserResolver userResolver; // provides the current user ID securely

    public UserProfileService(DynamoDbEnhancedClient enhancedClient, UserResolver userResolver) {
        this.enhancedClient = enhancedClient;
        this.userResolver = userResolver;
    }

    public UserProfile getProfile(String requestedUserId) {
        String currentUserId = userResolver.currentUserId()
            .orElseThrow(() -> new AccessDeniedException("Unauthenticated"));
        if (!currentUserId.equals(requestedUserId)) {
            throw new AccessDeniedException("Cannot access other user’s profile");
        }

        TableSchema schema = TableSchema.fromBean(UserProfile.class);
        GetItemEnhancedRequest request = GetItemEnhancedRequest.builder()
            .key(Key.builder().partitionValue(requestedUserId).build())
            .build();
        UserProfile profile = enhancedClient.table("UserProfile", schema).getItem(request);
        if (profile == null) {
            throw new NoSuchElementException("Profile not found");
        }
        return profile;
    }
}

For queries that might return multiple items, filter by the owner attribute at the DynamoDB level or enforce it in your application after retrieval. Here’s an example of scanning or querying with an explicit owner filter:

@Service
public class NoteService {

    private final DynamoDbTable noteTable;
    private final UserResolver userResolver;

    public NoteService(DynamoDbEnhancedClient enhancedClient, UserResolver userResolver) {
        this.noteTable = enhancedClient.table("Note", TableSchema.fromBean(NoteItem.class));
        this.userResolver = userResolver;
    }

    public List listNotesForCurrentUser() {
        String userId = userResolver.currentUserId()
            .orElseThrow(() -> new AccessDeniedException("Unauthenticated"));

        // Query with a GSI on ownerId for efficient filtering
        KeyConditionExpression keyCondition = KeyConditionExpression.of(
            b -> b.partitionKey("ownerId", userId)
        );
        QueryConditional conditional = QueryConditional.sortKey(keyCondition);
        PageIterable results = noteTable.query(r -> r.queryConditional(conditional));
        return results.stream().toList();
    }
}

Additionally, avoid exposing AWS credentials to browser contexts by ensuring tokens are handled server-side and not returned to the client. Validate and sanitize all inputs before using them in DynamoDB requests to prevent injection-style issues at the data layer, and enforce least-privilege IAM policies so that the application’s credentials can only access the required tables and operations.

By combining precise CORS configuration with per-request ownership checks and least-privilege IAM, you reduce the window of exposure when DynamoDB backs your Spring Boot API. These concrete changes align CORS policy with backend authorization, preventing cross-origin abuse while keeping data access tightly scoped to the authenticated user.