Insecure Deserialization in Axum with Cockroachdb

Insecure deserialization occurs when an application reconstructs objects from untrusted data without sufficient validation. In an Axum service that uses Cockroachdb as the backend, this typically arises when session state, authentication tokens, or API payloads are serialized (for example with serde and bincode or serde_json) and later deserialized on the server or client. If an attacker can supply crafted serialized bytes, they may trigger unexpected behavior during deserialization, such as type confusion or arbitrary code execution when the deserialization logic invokes methods or reconstructs complex types.

When Axum endpoints interact with Cockroachdb, developers sometimes store serialized objects directly in the database (for instance, a column with type BYTEA or a JSONB column containing serialized structures). If the application later deserializes that data to reconstruct domain objects without verifying integrity or authenticity, the deserialization path becomes an attack surface. Cockroachdb does not validate the semantics of stored bytes; it returns what was saved. Therefore, if Axum saves user-influenced serialized data and later reconstructs it, an attacker who can influence what is stored (through injection, compromised client state, or a malicious API request) can supply malicious payloads that are deserialized with elevated logic paths.

Common patterns that increase risk include using language-specific serialization formats that allow arbitrary type reconstruction (e.g., Java serialization–like behaviors via unsafe serde choices or custom deserializers) and storing deserialized state in server-side sessions or caches. In Axum, handlers that directly deserialize request bodies or database rows into structs without schema validation or integrity checks can inadvertently execute attacker-controlled logic during deserialization. This is especially relevant when the handler merges database rows from Cockroachdb with serialized metadata, since mismatched assumptions about types can lead to gadget chains or type confusion within the deserialization process.

Real-world attack patterns mirror OWASP API Top 10 API1:2023 — Broken Object Level Authorization and API1:2023 — Improper Asset Management, where insecure deserialization enables bypassing authorization or tampering with object references. For example, an attacker might alter a serialized identifier that maps to a Cockroachdb row to escalate privileges or access other users’ data. Since middleBrick tests such scenarios across 12 parallel checks including BOLA/IDOR and Input Validation, it can surface insecure deserialization risks that intersect with database interactions.

To detect this in practice, a scanner like middleBrick can present crafted serialized inputs to an Axum endpoint that reads and deserializes data from Cockroachdb, observing whether the server executes unexpected behavior or exposes sensitive information in responses. The tool does not fix the code; it provides findings with severity, context, and remediation guidance so developers can harden the deserialization path, validate inputs, and avoid storing or reconstructing untrusted serialized data.

Remediation focuses on avoiding deserialization of untrusted data, using strongly typed schemas, and validating all inputs before they reach database operations in Axum. Below are concrete patterns and code examples for safely interacting with Cockroachdb while mitigating insecure deserialization risks.

• Prefer schema‑validated data formats: Use JSON or Protocol Buffers with explicit schemas and avoid language‑native serialization for untrusted input. For example, store and retrieve data as JSONB and validate with serde_json::from_str against a strict struct.

use axum::{routing::post, Router};
use serde::{Deserialize, Serialize};
use sqlx::postgres::PgPoolOptions;
use sqlx::FromRow;

#[derive(Serialize, Deserialize, Debug, FromRow)]
struct UserProfile {
    id: i64,
    email: String,
    settings_json: serde_json::Value, // store settings as JSONB
}

async fn create_user_profile(
    pool: &sqlx::PgPool,
    email: String,
    settings: serde_json::Value,
) -> Result {
    sqlx::query_as("INSERT INTO user_profiles (email, settings) VALUES ($1, $2) RETURNING id, email, settings")
        .bind(email)
        .bind(settings)
        .fetch_one(pool)
        .await
}

• Do not use binary deserialization for attacker‑controlled data: If you must store serialized objects in Cockroachdb (e.g., in a BYTEA column), ensure the data is signed and verified before deserialization, and restrict the set of acceptable types. Treat database rows as untrusted when reconstructing objects.

use ring::signature::{self, UnparsedPublicKey, ED25519};

/// Verify a signed payload before deserialization.
fn verify_and_deserialize(data: &[u8], sig: &[u8], peer_public_key: &[u8; 32]) -> Result<MyStruct, &'static str> {
    let public_key = UnparsedPublicKey::new(&ED25519, peer_public_key);
    public_key.verify(data, sig).map_err(|_| "Verification failed")?;
    bincode::deserialize(data).map_err(|_| "Deserialization failed")
}

• Apply principle of least privilege and row‑level security in Cockroachdb: Use database roles and policies so that Axum connections can only access rows the application user is allowed to see. This limits the impact of any deserialization issue that might lead to unauthorized data reconstruction.

-- Example Cockroachdb role and policy (run separately, not from Axum)
CREATE USER axum_app WITH PASSWORD 'strong_password';
GRANT SELECT, INSERT ON TABLE user_profiles TO axum_app;
ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT ON TABLES TO axum_app;
-- Row-level policy example using tenant_id column
CREATE POLICY tenant_isolation ON user_profiles FOR SELECT USING (tenant_id = current_setting('app.tenant_id')::INT);

• Use middleware to validate and sanitize inputs before handlers: In Axum, extract and validate data early, and only pass safe, typed structures to database logic.

use axum::{extract::State, http::StatusCode, response::IntoResponse};
use serde::Deserialize;

#[derive(Deserialize)]
struct CreateUser {
    email: String,
    // other fields validated by schema
}

async fn create_user_handler(
    State(pool): State<sqlx::PgPool>,
    axum::extract::Json(payload): axum::extract::Json<CreateUser>,
) -> Result<impl IntoResponse, (StatusCode, String)> {
    // Validate email format, length, etc., before DB interaction
    if payload.email.is_empty() {
        return Err((StatusCode::BAD_REQUEST, "email required".to_string()));
    }
    // Proceed with safe, typed SQLx calls
    Ok(StatusCode::CREATED)
}

By combining strict input validation, schema‑driven data formats, and careful database configuration, you reduce the attack surface associated with insecure deserialization in Axum applications that rely on Cockroachdb.