Out Of Bounds Write in Axum with Cockroachdb

An Out Of Bounds Write occurs when data is written to a memory location outside the intended allocation. In an Axum application that uses CockroachDB as the backend, this typically surfaces at the API boundary when user-controlled input is used to size buffers, deserialize payloads, or drive pagination or batch operations that eventually feed SQL statements sent to CockroachDB. Even though CockroachDB itself is a resilient database, the vulnerability is introduced in the Axum service layer through unchecked input that affects how data is prepared or sent to the database.

Consider an endpoint that accepts a page size parameter to control how many rows are fetched from CockroachDB. If the Axum handler does not validate the page size, a large integer can cause the service to allocate an oversized in-memory buffer to stage results before sending them to CockroachDB or to the client. This buffer can overflow, leading to corrupted memory, unexpected behavior, or potential code execution within the Axum process. Similarly, deserialization of JSON or form data into Rust structs without proper bounds checking can cause writes beyond allocated slices when constructing values that are later passed to CockroachDB queries.

The risk is compounded when the Axum service builds SQL dynamically using string concatenation or query builders influenced by unchecked user input. Although CockroachDB uses parameterized queries to prevent SQL injection, an Out Of Bounds Write in the Axum layer can corrupt the process memory that holds query templates or metadata, indirectly affecting the integrity of statements sent to CockroachDB. This does not mean CockroachDB is at fault; rather, the Axum application must ensure that all inputs influencing memory allocations and query construction are strictly bounded and validated before any interaction with the database.

In practice, this vulnerability manifests when the Axum service receives crafted payloads that exploit missing checks on arrays, vectors, or buffers. For example, an attacker might supply a negative or extremely large value for an expected small numeric parameter, causing the Axum handler to allocate a buffer of unexpected size or iterate beyond valid indices. Because the scan reports from middleBrick include unchecked input validation and unsafe consumption findings, teams can identify these risky patterns early when endpoints accept unbounded user input that influences how data is staged or sent to CockroachDB.

middleBrick can detect such issues by analyzing the OpenAPI specification and runtime behavior of the Axum endpoints, highlighting missing input validation and unsafe consumption patterns that could lead to memory corruption when handling requests directed at CockroachDB. Developers should rely on precise validation, bounded collections, and strict schema checks in Axum to ensure that no out of bounds writes occur before any database operation reaches CockroachDB.

Remediation centers on strict input validation, bounded data structures, and safe handling of data before it is used in CockroachDB interactions. In Axum, use strong typing for route parameters and query inputs, and enforce limits explicitly before constructing queries or buffers that will be sent to CockroachDB.

For pagination, always validate page and page_size against reasonable bounds. Here is an example of a safe handler in Axum that limits page size and ensures safe database interaction with CockroachDB:

use axum::extract::Query;
use serde::Deserialize;

#[derive(Deserialize)]
struct PaginatedParams {
    page: Option,
    page_size: Option,
}

async fn list_items(Query(params): Query) -> Result {
    let page = params.page.unwrap_or(1);
    let page_size = params.page_size.unwrap_or(10);

    // Enforce bounds to prevent out of bounds allocations
    if page_size == 0 || page_size > 100 {
        return Err((StatusCode::BAD_REQUEST, "page_size must be between 1 and 100".to_string()));
    }

    let offset = (page - 1) * page_size;

    // Use a parameterized query to CockroachDB
    let rows = sqlx::query("SELECT id, name FROM items LIMIT $1 OFFSET $2")
        .bind(page_size as i64)
        .bind(offset as i64)
        .fetch_all(&pool)
        .await
        .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, e.to_string()))?;

    Ok(axum::Json(rows))
}

This pattern ensures that page_size is bounded before it is used in arithmetic and passed as a parameter to CockroachDB, preventing out of bounds write risks that could stem from unchecked user input.

When deserializing complex payloads, prefer strongly typed structures and avoid raw mutable buffers. For example, if you need to stage data before sending it to CockroachDB, use fixed-size arrays or collections with explicit capacity limits:

use axum::Json;
use serde::Deserialize;

#[derive(Deserialize)]
struct ItemInput {
    name: String,
    tags: Vec,
}

async fn create_item(Json(payload): Json) -> Result {
    // Validate collection sizes to avoid excessive memory use
    if payload.tags.len() > 50 {
        return Err((StatusCode::BAD_REQUEST, "too many tags".to_string()));
    }

    // Build a parameterized insert for CockroachDB
    sqlx::query("INSERT INTO items (name, tags) VALUES ($1, $2)")
        .bind(&payload.name)
        .bind(&payload.tags)
        .execute(&pool)
        .await
        .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, e.to_string()))?;

    Ok(StatusCode::CREATED)
}

By validating the length of tags and using parameterized statements, the Axum service avoids unbounded writes into memory and ensures safe interaction with CockroachDB. These practices align with the kind of input validation and unsafe consumption findings that middleBrick reports, helping teams address issues before they reach production.

Additionally, ensure that any buffer or temporary storage used to batch statements for CockroachDB has fixed maximum sizes and is never sized by unchecked user values. Combining explicit bounds in Rust types, strict validation in Axum extractors, and parameterized SQL provides a robust defense against Out Of Bounds Write vulnerabilities in this stack.