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Description

This error indicates that the MongoDB server rejected a connection attempt due to invalid authentication credentials. It commonly occurs when a client tries to connect to a MongoDB instance with an incorrect username, password, or an unauthorized user.

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Error Message

Authentication Failed

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Known Causes

4 known causes

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Incorrect Username or Password

The provided username or password does not match any existing user's credentials on the MongoDB server.

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User Does Not Exist

The specified user account has not been created or does not exist in the authentication database.

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Incorrect Authentication Database

The client is attempting to authenticate against a database different from where the user account was defined or authorized.

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Authentication Mechanism Mismatch

The client and server are configured to use different authentication mechanisms (e.g., SCRAM-SHA-1 vs. SCRAM-SHA-256), leading to a handshake failure.

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Solutions

5 solutions available

1. Verify Credentials easy

Check username and password are correct

1

Test connection

mongosh --host localhost -u username -p password --authenticationDatabase admin

2

Reset password if forgotten

// Connect as admin
use admin
db.changeUserPassword("username", "newpassword")

2. Check Authentication Database easy

User might be in different database

1

Find user in system

use admin
db.system.users.find({ user: "myuser" })

2

Specify correct authSource

// If user is in 'admin' database:
mongosh "mongodb://user:pass@host/mydb?authSource=admin"

// If user is in 'mydb' database:
mongosh "mongodb://user:pass@host/mydb?authSource=mydb"

3. Check Authentication Mechanism medium

Ensure client uses correct auth method

1

Check server auth mechanism

db.adminCommand({ getParameter: 1, authenticationMechanisms: 1 })

2

Specify mechanism in connection

mongosh "mongodb://user:pass@host/db?authMechanism=SCRAM-SHA-256"

4. Create Missing User easy

User might not exist

1

Create user

use admin
db.createUser({
  user: "newuser",
  pwd: "password",
  roles: [{ role: "readWrite", db: "mydb" }]
})

5. Fix Connection String Encoding easy

Special characters need URL encoding

1

URL encode special characters in password

// If password is: p@ss:word/123
// Encode as: p%40ss%3Aword%2F123

mongosh "mongodb://user:p%40ss%3Aword%2F123@host/db"

2

Common encodings

// @ = %40
// : = %3A
// / = %2F
// # = %23
// ? = %3F

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Related Errors

5 related errors

MongoDB Error 18: Authentication Failed