Broken Access Control in Actix with Mongodb

Broken Access Control occurs when Actix routes rely on application-level checks instead of enforcing authorization on every request, and when route handlers query Mongodb without validating that the authenticated actor is permitted to access the targeted document. In a typical Actix-web service, a route might extract a user identifier from a JWT, then build a Mongodb filter using that identifier. If the filter is incomplete or missing, an unauthenticated or low-privilege actor can manipulate path or query parameters to request another user’s resource, resulting in IDOR/BOLA.

Consider an endpoint like /users/{user_id}/profile. If the handler only checks that a user is authenticated but constructs a Mongodb query such as { "_id": user_id } using the path parameter directly, and the parameter is not cross-checked against the identity encoded in the token, an attacker can change {user_id} to another valid ObjectId and retrieve or modify data they should not see. This becomes more impactful when Mongodb documents contain sensitive fields or when update operations do not re-validate ownership before applying changes.

Additionally, Actix middleware or guards may be misconfigured so that some routes are reachable without proper authentication, exposing unauthenticated attack surface. If authorization logic is scattered across services or duplicated across handlers, inconsistencies arise: one handler might enforce ownership, another might not. In combination with Mongodb’s flexible document model, missing field-level checks (for example, missing tenant or role attributes) can allow horizontal privilege escalation across records that share the same collection.

Another vector involves unsafe operations like find_one_and_update without re-checking ownership after the filter. An attacker could leverage Insecure Direct Object References (IDOR) to update another user’s profile or elevate permissions stored in the document if the update does not validate the actor’s rights against the document’s internal references.

Because middleBrick scans the unauthenticated attack surface and tests endpoints including those backed by Mongodb, it can identify missing authentication on routes, missing resource-level authorization, and inconsistent authorization patterns across handlers. The scanner also checks for data exposure and encryption issues that may amplify the impact of broken access control when sensitive fields are returned or transmitted without encryption.

Remediation focuses on ensuring every route enforces ownership or role-based access using data from the authenticated context, not just the path parameters, and that Mongodb queries incorporate the actor’s identity explicitly. Use Actix extractors to obtain the authenticated subject, then build queries that include both the subject identifier and any tenant or scope fields.

Example: a profile endpoint that safely scopes queries to the requesting user.

use actix_web::{web, HttpResponse, Result};
use mongodb::{bson::{doc, oid::ObjectId}};
use serde::{Deserialize, Serialize};

#[derive(Serialize, Deserialize)]
struct UserProfile {
    #[serde(rename = "_id")]
    id: ObjectId,
    username: String,
    email: String,
}

async fn get_profile(
    user_id: web::Path,
    claims: actix_identity::Identity, // authenticated identity
    coll: web::Data>,
) -> Result {
    let subject = claims.id().ok_or_else(|| actix_web::error::ErrorUnauthorized("missing identity"))?;
    // Ensure the path parameter is a valid ObjectId
    let requested_id = ObjectId::parse_str(&user_id).map_err(|_| actix_web::error::ErrorBadRequest("invalid id"))?;
    // Critical: scope query by both subject and requested id
    let filter = doc! {
        "_id": requested_id,
        "user_id": subject, // field that stores the subject id in the document
    };
    let maybe_doc = coll.find_one(filter, None).await.map_err(|e| actix_web::error::ErrorInternalServerError(e))?;
    match maybe_doc {
        Some(doc) => Ok(HttpResponse::Ok().json(doc)),
        None => Ok(HttpResponse::NotFound().body("not found or access denied")),
    }
}

For updates, re-validate ownership within the operation and avoid upserts that could inadvertently create records across scopes.

async fn update_email(
    user_id: web::Path,
    claims: actix_identity::Identity,
    coll: web::Data>,
    body: web::Json,
) -> Result {
    let subject = claims.id().ok_or_else(|| actix_web::error::ErrorUnauthorized("missing identity"))?;
    let requested_id = ObjectId::parse_str(&user_id).map_err(|_| actix_web::error::ErrorBadRequest("invalid id"))?;
    let update = doc! {
        "$set": {
            "email": body["email"].as_str().ok_or_else(|| actix_web::error::ErrorBadRequest("invalid email"))?,
        }
    };
    // Filter includes ownership proof
    let filter = doc! {
        "_id": requested_id,
        "user_id": subject,
    };
    let result = coll.find_one_and_update(filter, update, None).await.map_err(|e| actix_web::error::ErrorInternalServerError(e))?;
    match result {
        Some(_) => Ok(HttpResponse::Ok().finish()),
        None => Ok(HttpResponse::NotFound().body("not found or access denied")),
    }
}

In more complex scenarios, embed tenant or organization identifiers in documents and include them in every filter. Enforce role-based access by checking claims against a role field stored in the document or a related collection, and avoid exposing endpoints that do not validate the combination of path parameters, authenticated identity, and document-level attributes.

middleBrick can support this remediation workflow by scanning your endpoints and identifying routes where filters do not include subject-level scoping or where unauthenticated access is possible. The scanner maps findings to frameworks such as OWASP API Top 10 and provides prioritized remediation guidance to tighten authorization around Mongodb-backed resources.