Dangling Dns in Chi with Dynamodb

A dangling DNS record in a Chi environment can expose an AWS DynamoDB endpoint that is intended to be internal or restricted. When a custom domain or alias points to a load balancer, API Gateway, or another intermediary that forwards traffic to DynamoDB, misconfiguration may leave the underlying table reachable through an unintended path. If the DNS record is not updated or removed during infrastructure changes, it remains resolvable and may direct requests to an endpoint that still accepts authenticated calls, bypassing expected network-level restrictions.

In a Chi-based service that integrates with DynamoDB via the AWS SDK for .NET, the application typically uses the AWS SDK to sign requests with IAM credentials. If the DNS entry for the endpoint used by the SDK is not aligned with the intended VPC endpoint or private link configuration, requests may route over the public internet. This can expose the table to internet-facing threats if the table policy or resource-based policy does not explicitly restrict access to expected VPCs or IAM roles. Attackers who discover the dangling DNS name might attempt to probe the endpoint, and if weak authentication, an open table policy, or misconfigured IAM roles exist, they could perform unauthorized read or write operations, leading to sensitive data exposure or data modification.

The combination is particularly risky when the DynamoDB table stores sensitive data and relies on network-level controls that assume a fixed, private endpoint. Because Chi services often manage HTTP routing and middleware pipelines, developers might overlook DNS configuration when refactoring or decommissioning services. The table itself does not know about DNS; it only sees requests arriving at a given endpoint. If that endpoint becomes reachable from broader networks due to a dangling record, the table’s security posture depends entirely on IAM policies and VPC boundaries. Without precise policy conditions that limit source IP ranges or require VPC endpoint restrictions, an attacker can exploit the mismatch between DNS routing and intended network segmentation.

middleBrick scans such configurations by testing the unauthenticated attack surface and cross-referencing OpenAPI specs with runtime behavior. When a dangling DNS name resolves to an API endpoint that interacts with DynamoDB, the scanner can identify unexpected exposure and highlight related IAM and network misconfigurations. This capability is valuable for detecting subtle routing issues that do not appear in standard configuration reviews but can lead to significant data exposure.

Remediation focuses on strict endpoint alignment, least-privilege IAM, and explicit network controls. Ensure that the DNS records used by your Chi application point only to intended endpoints, and remove or archive any obsolete entries. For DynamoDB access, avoid wide-open table policies and prefer resource-based policies that restrict by VPC endpoint, IAM role, and source IP where applicable.

In your Chi application, configure the AWS SDK to use a specific endpoint configuration that matches your intended network path. If you use DynamoDB Local for testing, ensure the production configuration does not accidentally point to a local or unintended endpoint. The following example shows how to explicitly set the service URL and region in a Chi project using the AWS SDK for .NET, reducing the risk of accidental routing to a wrong endpoint:

using Amazon.DynamoDBv2;
using Amazon.DynamoDBv2.Model;

var config = new AmazonDynamoDBConfig
{
    ServiceURL = "https://dynamodb.us-east-1.amazonaws.com",
    RegionEndpoint = Amazon.RegionEndpoint.USEast1
};

using var client = new AmazonDynamoDBClient(config);

var request = new DescribeTableRequest
{
    TableName = "MySecureTable"
};

var response = await client.DescribeTableAsync(request);

Equally important is to enforce least-privilege IAM policies for the role or user your Chi service assumes. Instead of allowing dynamodb:*, scope actions to required operations and constrain resources with conditions. The following IAM policy example grants read-only access to a specific table only when requests come from an approved VPC endpoint and use TLS:

{ 
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "dynamodb:GetItem",
        "dynamodb:Query",
        "dynamodb:Scan"
      ],
      "Resource": "arn:aws:dynamodb:us-east-1:123456789012:table/MySecureTable",
      "Condition": {
        "StringEquals": {
          "aws:SourceVpce": "vpce-abc123"
        },
        "Bool": {
          "aws:SecureTransport": "true"
        }
      }
    }
  ]
}

Finally, validate DNS configurations as part of your deployment pipeline. Remove dangling records and verify that the endpoint used by your Chi service matches the intended target. Combine this with continuous monitoring of access patterns and IAM usage to detect anomalies. middleBrick Pro plan supports continuous monitoring and can alert you if a scan detects unexpected exposure related to DNS or IAM misconfigurations, helping you maintain a secure posture without manual oversight.