CWE

Overly Restrictive Account Lockout Mechanism

ID: 645		Date: (C)2012-05-14   (M)2022-10-10
Type: weakness		Status: INCOMPLETE
Abstraction Type: Base

Description

The software contains an account lockout protection mechanism, but the mechanism is too restrictive and can be triggered too easily. This allows attackers to deny service to legitimate users by causing their accounts to be locked out.

Extended Description

Account lockout is a security feature often present in applications as a countermeasure to the brute force attack on the password based authentication mechanism of the system. After a certain number of failed login attempts, the users' account may be disabled for a certain period of time or until it is unlocked by an administrator. Other security events may also possibly trigger account lockout. However, an attacker may use this very security feature to deny service to legitimate system users. It is therefore important to ensure that the account lockout security mechanism is not overly restrictive.

Enabling Factors for Exploitation
The system has an account lockout mechanism.
An attacker must be able to trigger the account lockout mechanism.
The cost to the attacker of triggering the account lockout mechanism should be less than the cost to re-enable the account.

Likelihood of Exploit: High

Applicable Platforms
Language Class: All

Time Of Introduction

• Architecture and Design

Common Consequences

Scope	Technical Impact	Notes
Availability	DoS: resource consumption (other)	Users could be locked out of accounts.

Detection Methods
None

Potential Mitigations

Phase	Strategy	Description	Effectiveness	Notes
Architecture and Design		Implement more intelligent password throttling mechanisms such as those which take IP address into account, in addition to the login name.
Architecture and Design		Implement a lockout timeout that grows as the number of incorrect login attempts goes up, eventually resulting in a complete lockout.
Architecture and Design		Consider alternatives to account lockout that would still be effective against password brute force attacks, such as presenting the user machine with a puzzle to solve (makes it do some computation).

Relationships

Related CWE	Type	View	Chain
CWE-645 ChildOf CWE-898	Category	CWE-888

Demonstrative Examples
None

Observed Examples

1. : A famous example of this type an attack is the eBay attack. eBay always displays the user id of the highest bidder. In the final minutes of the auction, one of the bidders could try to log in as the highest bidder three times. After three incorrect log in attempts, eBay password throttling would kick in and lock out the highest bidder's account for some time. An attacker could then make their own bid and their victim would not have a chance to place the counter bid because they would be locked out. Thus an attacker could win the auction.

For more examples, refer to CVE relations in the bottom box.

White Box Definitions
None

Black Box Definitions
None

Taxynomy Mappings
None

References:
None