Weak Password Recovery Mechanism for Forgotten Password
Weakness ID: 640 (Weakness Base)Status: Incomplete
+ Description

Description Summary

The software contains a mechanism for users to recover or change their passwords without knowing the original password, but the mechanism is weak.

Extended Description

It is common for an application to have a mechanism that provides a means for a user to gain access to their account in the event they forget their password. Very often the password recovery mechanism is weak, which has the effect of making it more likely that it would be possible for a person other than the legitimate system user to gain access to that user's account.

This weakness may be that the security question is too easy to guess or find an answer to (e.g. because it is too common). Or there might be an implementation weakness in the password recovery mechanism code that may for instance trick the system into e-mailing the new password to an e-mail account other than that of the user. There might be no throttling done on the rate of password resets so that a legitimate user can be denied service by an attacker if an attacker tries to recover their password in a rapid succession. The system may send the original password to the user rather than generating a new temporary password. In summary, password recovery functionality, if not carefully designed and implemented can often become the system's weakest link that can be misused in a way that would allow an attacker to gain unauthorized access to the system. Weak password recovery schemes completely undermine a strong password authentication scheme.

+ Time of Introduction
  • Architecture and Design
  • Implementation
+ Applicable Platforms



+ Common Consequences

An attacker gains unauthorized access to the system by retrieving legitimate user's authentication credentials

An attacker denies service to legitimate system users by launching a brute force attack on the password recovery mechanism using user ids of legitimate users

The system's security functionality is turned against the system by the attacker.

+ Likelihood of Exploit


+ Enabling Factors for Exploitation

The system allows users to recover their passwords and gain access back into the system.

Password recovery mechanism relies only on something the user knows and not something the user has.

Weak security questions are used.

No third party intervention is required to use the password recovery mechanism.

+ Observed Examples
A famous example of this type of weakness being exploited 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.
+ Potential Mitigations

Make sure that all input supplied by the user to the password recovery mechanism is thoroughly filtered and validated

Do not use standard weak security questions and use several security questions.

Make sure that there is throttling on the number of incorrect answers to a security question. Disable the password recovery functionality after a certain (small) number of incorrect guesses.

Require that the user properly answers the security question prior to resetting their password and sending the new password to the e-mail address of record.

Never allow the user to control what e-mail address the new password will be sent to in the password recovery mechanism.

Assign a new temporary password rather than revealing the original password.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory255Credentials Management
Development Concepts (primary)699
ChildOfWeakness ClassWeakness Class693Protection Mechanism Failure
Research Concepts (primary)1000
ChildOfCategoryCategory724OWASP Top Ten 2004 Category A3 - Broken Authentication and Session Management
Weaknesses in OWASP Top Ten (2004) (primary)711
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
WASC49Insufficient Password Recovery
+ Related Attack Patterns
CAPEC-IDAttack Pattern Name
(CAPEC Version: 1.4)
50Password Recovery Exploitation
+ Maintenance Notes

This entry might be reclassified as a category or "loose composite," since it lists multiple specific errors that can make the mechanism weak. However, under view 1000, it could be a weakness under protection mechanism failure, although it is different from most PMF issues since it is related to a feature that is designed to bypass a protection mechanism (specifically, the lack of knowledge of a password).

This entry probably needs to be split; see extended description.

+ Content History
Submission DateSubmitterOrganizationSource
2008-01-30Evgeny LebanidzeCigitalExternal Submission
Modification DateModifierOrganizationSource
2008-09-08CWE Content TeamMITREInternal
updated Common Consequences, Description, Maintenance Notes, Name, Relationships
2009-03-10CWE Content TeamMITREInternal
updated Relationships
2009-05-27CWE Content TeamMITREInternal
updated Related Attack Patterns
Previous Entry Names
Change DatePrevious Entry Name
2008-09-09Weak Password Recovery Mechanism