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Detecting NoSQL Injection

NoSQL, means “not only SQL,” refers to a broad category of database technologies that are intended to manage huge volumes of unstructured and semi-structured data.
SQL Injection is an evergreen vulnerability being discovered on a regular basis in enterprise products and open source libraries as shown by the below chart. Apart from SQL Injection, there are multiple types of injection vulnerabilities such as Command Injection, Nosql injection, OS injection, HTML injection etc.

Over the past 10 years, NoSQL databases have become potent substitutes for conventional relational databases in the rapidly changing field of data management. NoSQL databases are now the foundation of many contemporary applications because of their scalability, flexibility, and adaptability to different data structures. But tremendous power also comes with great responsibility, and noSQL injection is a hidden menace that one needs to be extremely cautious of.

What is NoSQL?

The phrase NoSQL, which means “not only SQL,” refers to a broad category of database technologies that are intended to manage huge volumes of unstructured and semi-structured data. With NoSQL databases, data storage is made possible by a schema-less methodology, in contrast to traditional relational databases, which rely on the structured query language (SQL).


Types of NoSQL Databases:

  • Document-oriented databases (e.g., MongoDB): Store data in flexible, JSON-like documents.
  • Key-value stores (e.g., Redis): Simple key-value pairs for efficient data storage.
  • Column-family stores (e.g., Apache Cassandra): Organize data into columns for scalability.
  • Graph databases (e.g., Neo4j): Designed for intricate relationships in data.What is NoSQL?

What is NoSQL Injection?

NoSQL injection is a security vulnerability that arises when attackers exploit weaknesses in an application’s input validation and query construction, allowing them to manipulate NoSQL database queries. Similar to SQL injection in relational databases, this attack vector can lead to unauthorized access, data manipulation, and potentially catastrophic breaches.

Detecting NoSQL Injection

Using the scan tool is a great way to find some injectable strings, but to extract data, it’s important to understand the types of injections possible with NoSQL systems, and how they present.  This blog contains the various ways that you might determine if injections are possible, focusing primarily on the most popular NoSQL database, Mongo. From simplest to hardest:
  • Error based injection (when the server returns a clear NoSQL error)
  • Blind boolean based injection (When the server evaluates a statement as true or false)
  • Timing Injections.

Injecting Payloads

Anywhere you might expect to see SQL injection, you can potentially find nosql injection. consider URL parameters, POST parameters, and even sometimes HTTP headers.
GET requests can often be typed into the browser directly by adding nosql into the URL directly:

  1. || ‘1’==’1

POST requests generally need to be intercepted and modified, as NoSQL often includes JSON object structures.

  1. {“username”: “user”, “password”: “pass”}  would change to
    {“username”: {“ne”: “fakeuser”}, password: “pass”}
  1. {“$where”:  “return true”}

Each NoSQL system may have it’s own syntax, but mongo allows for both JSON (Technically BSON, but that generally happens under the hood server side) and JavaScript. JS can run directly in the Mongo server if passed through functions that allow it, and JS is enabled on the server (it is enabled by default).
If you already understand SQL injection, the concepts here are mostly the same, and only the details differ.

Error Based NoSQL Injection

The simplest way to determine if injection is possible is to input some special noSQL characters, and see if the server returns an error. This might be a full error string indicating the NoSQL database in use, or something like a 500 error.


Plug this string into each GET parameter to see if an error occurs
Replace elements in posted JSON contents with these special characters, or NoSQL keywords like $ne, $eq, $where, $or, etc to see if there are errors.
Send additional objects along with valid JSON. For instance {“user”: “nullsweep”} could become {“user”: [“nullsweep”, “foo”]} or {“$or”: [{“user”: “foo”}, {“user”: “realuser”}]}
Some of these characters may also trigger other injection vulnerabilities (JS injection, SQL injection, shell injection, etc), so further testing may be needed to ensure it is a NoSQL backend.

Blind Boolean Injection

If sending special characters doesn’t cause the site to send error information, it may still be possible to find an injection by sending boolean expressions (a true or false result) if the page changes depending on the answer. For instance, a product page with a product ID parameter that is injectable may return product details for one query, but a product not found message otherwise.

A backend query that is looking up a product by doing something like “id = $id” might use a query like db.product.find( {“id”: 5} ). Ideally, we would want to control the whole query to inject something always false such as db.product.find( {“$and”: [ {“id”: 5}, {“id”: 6} ]. It isn’t always possible to inject operators like $and and $or because the operators preceed the field labels.
Instead, we may have to try a few different things. We could try to make the query match everything but the ID 5: db.product.find( {“id”: {“$ne”: 5} } ) or use the $in or $nin operators such as db.product.find( {“id”: {“$in”: []} }) to ensure returning no data.
If the injection is successful, you will see a difference between the ‘true’ version and ‘false’ version.

The Boolean Injection Cheat Sheet:

  • {“$ne”: -1}
  • {“$in”: []}
  • {“$and”: [ {“id”: 5}, {“id”: 6} ]}
  • {“$where”:  “return true”}
  • {“$or”: [{},{“foo”:”1″}]}
  • || ‘1’==’1
  •;return true

You may need to try appending certain characters to correctly terminate the query:

  • //
  • %00
  • ”     
  • some number of closing brackets or braces, in some combination

Timing Based Injection

Sometimes, even when injection is possible and the attacker has sent valid true and false values, the page response is identical, and it can’t be determined if an injection was successful or not.
In these cases, we can still try to determine if an injection takes place by asking the NoSQL instance to pause for a period of time before returning results, and detecting the resulting difference in time as the proof of successful injection. Timing injection is identical to blind boolean injection, except instead of trying to get the page to return true or false values, we try to get the page load more slowly (for true) or quickly (for false).
You will likely need several page loads to gather baseline timing information before beginning the injection. The longer sleep times used in this injection type, the easier it is to spot in the results, but the longer it will take to gather information.
Timing injections are only possible where JS can be executed in the database, and can lead to other interesting attacks.

Timing NoSql Injection Cheat Sheet:

  • {“$where”:  “sleep(100)”}
  • ;sleep(100);

NoSQL Injection Limitations

Unlike SQL injection, finding that a site is injectable may not give unfettered access to the data. How the injection presents may allow full control over the backend, or limited querying ability on a single schema. Because records don’t follow a common structure, discovering the structure can prove an additional challenge when exploiting these types of vulnerabilities.

How Do I Prevent It?

Here are some measures to prevent  NoSQL injection attacks, or minimize the impact if it happens:

  • Prepared Statements: For NoSQL calls, use prepared statements instead of building dynamic queries using string concatenation.
  • Input Validation: Validate inputs to detect malicious values. For NoSQL databases, also validate input types against expected types
  • Least Privilege: To minimize the potential damage of a successful injection attack, do not assign DBA or admin type access rights to your application accounts. Similarly, minimize the privileges of the operating system account that the database process runs under.
  • Regular Audits and Testing: Frequently audit your application, conduct security testing, and stay vigilant for potential vulnerabilities.


Understanding the nuances of NoSQL databases, identifying NoSQL injection threats, and employing robust preventive measures are integral components of securing your application and its underlying data. Stay informed, remain proactive with security practices, and fortify your defenses against the ever-persistent specter of NoSQL injection.

By: FireCompass Delivery Team – Arnab Chattopadhyay, Amit Da, Joy Sen, Komma Uma Maheswar Reddy

About FireCompass:

FireCompass is a SaaS platform for Continuous Automated Pen Testing, Red Teaming  and External Attack Surface Management (EASM). FireCompass continuously indexes and monitors the deep, dark and surface webs using nation-state grade reconnaissance techniques. The platform automatically discovers an organization’s digital attack surface and launches multi-stage safe attacks, mimicking a real attacker, to help identify breach and attack paths that are otherwise missed out by conventional tools.

Feel free to get in touch with us to get a better view of your attack surface.

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