Cors Wildcard in Aspnet with Cockroachdb

A CORS wildcard in an ASP.NET application that connects to CockroachDB can unintentionally expose database-driven endpoints to any origin. When app.UseCors(builder => builder.AllowAnyOrigin()) is used together with credentials or custom headers, browsers allow cross-origin requests that reach ASP.NET controller actions performing SQL operations against CockroachDB. Because CockroachDB often serves as the source of truth for user and tenant data, these permissive CORS rules can make it possible for a malicious site to trigger authenticated requests that read or modify records via the exposed API.

The risk is compounded when the API does not enforce strict origin checks after the CORS preflight passes. An attacker can craft frontend JavaScript that calls an endpoint like /api/accounts/{id}, and if the endpoint relies on identity claims or subdomain routing to select the CockroachDB tenant context, data from other tenants may be leaked. OWASP API Top 10:2023 A1 (Broken Object Level Authorization) and A5 (Security Misconfiguration) map to this pattern, as overly broad CORS can bypass intended isolation boundaries.

In a typical setup, the ASP.NET middleware pipeline processes CORS before routing to controllers that open a CockroachDB SQL connection. If the CORS policy allows any origin and the API uses a shared database user or connection string, an attacker who tricks a victim into making a request can cause the backend to run queries under the same permissions as the application. CockroachDB’s strong consistency does not protect against this class of issue; the exposure occurs at the API layer, but the impact is realized against the database when unauthorized queries are executed.

For example, consider an endpoint that includes the tenant ID in a SQL WHERE clause based on the request host. A wildcard CORS policy does not validate that the origin is trusted, so a request forged from an attacker-controlled site may still route to the same endpoint and retrieve rows belonging to other tenants if the authorization check is incomplete. This illustrates why CORS must be scoped to known origins and coupled with explicit resource-level authorization, especially when the backend stores sensitive data in CockroachDB.

To detect this using middleBrick, you can submit your ASP.NET endpoint URL for a scan. The tool runs checks for CORS misconfiguration alongside authentication, BOLA/IDOR, and other controls, providing a security risk score and prioritized findings with remediation guidance. It also maps findings to frameworks such as OWASP API Top 10 and PCI-DSS, helping you understand the compliance implications of permissive CORS in combination with CockroachDB-backed services.

Remediation focuses on tightening CORS policy and ensuring that each CockroachDB query respects the correct tenant and user context. Avoid AllowAnyOrigin() when credentials are involved; instead, specify exact origins and enable credentials only when necessary. Combine this with explicit authorization that validates the requesting user against the tenant stored in CockroachDB before executing SQL.

Use policy-based authorization in ASP.NET to ensure only approved origins can access sensitive endpoints. The following CORS configuration is more restrictive and suitable for production:

builder.Services.AddCors(options =>
{
    options.AddPolicy("AllowedOrigins", policy =>
    {
        policy.WithOrigins("https://app.yourdomain.com", "https://admin.yourdomain.com")
              .AllowAnyHeader()
              .WithMethods("GET", "POST", "PUT", "DELETE")
              .AllowCredentials();
    });
});
app.UseCors("AllowedOrigins");

On the CockroachDB side, always parameterize queries and enforce row-level security by tenant. The example below uses Npgsql with ASP.NET to open a connection and run a tenant-scoped query. Ensure the connection string is stored securely and that the application user in CockroachDB has least-privilege permissions.

using var conn = new NpgsqlConnection(Configuration.GetConnectionString("CockroachDB"));
await conn.OpenAsync();
var sql = "SELECT id, name, email FROM accounts WHERE tenant_id = @tenantId AND user_id = @userId LIMIT 100";
using var cmd = new NpgsqlCommand(sql, conn);
cmd.Parameters.AddWithValue("tenantId", tenantId);
cmd.Parameters.AddWithValue("userId", userId);
await using var reader = await cmd.ExecuteReaderAsync();
while (await reader.ReadAsync())
{
    // map results
}

For multi-tenant deployments, validate the tenant against the origin or a claim before using it in SQL. You can retrieve the tenant from claims or a subdomain and ensure it matches a row in CockroachDB:

var tenantId = claims.FirstOrDefault(c => c.Type == "tenant_id")?.Value;
if (string.IsNullOrEmpty(tenantId))
{
    return Results.Forbid();
}
var tenantExists = await TenantExistsInCockroachDB(conn, tenantId);
if (!tenantExists)
{
    return Results.StatusCode(403);
}

middleBrick’s scans include checks for CORS misconfiguration and authorization gaps. The Pro plan adds continuous monitoring so that if a deployment accidentally re-introduces a wildcard CORS rule, you receive alerts. The GitHub Action can fail builds when the score drops below your chosen threshold, preventing insecure CORS settings from reaching production alongside CockroachDB integrations.

By combining precise CORS policies with tenant-aware SQL and leveraging automation in CI/CD, you reduce the chance that a misconfigured wildcard exposes sensitive data stored in CockroachDB. The MCP Server also allows you to run these checks directly from AI coding assistants, helping catch issues earlier during development.