CWE-640: Weak Password Recovery Mechanism for Forgotten Password
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
Languages
All
Common Consequences
Scope
Effect
Access Control
Technical Impact: Gain privileges / assume
identity
An attacker could gain unauthorized access to the system by retrieving
legitimate user's authentication credentials.
An attacker could deny service to legitimate system users by launching
a brute force attack on the password recovery mechanism using user ids
of legitimate users.
Integrity
Other
Technical Impact: Other
The system's security functionality is turned against the system by
the attacker.
Likelihood of Exploit
High
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
Reference
Description
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
Phase: Architecture and Design
Make sure that all input supplied by the user to the password recovery
mechanism is thoroughly filtered and validated.
Phase: Architecture and Design
Do not use standard weak security questions and use several security
questions.
Phase: Architecture and Design
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.
Phase: Architecture and Design
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.
Phase: Architecture and Design
Never allow the user to control what e-mail address the new password
will be sent to in the password recovery mechanism.
Phase: Architecture and Design
Assign a new temporary password rather than revealing the original
password.
[REF-17] Michael Howard, David LeBlanc
and John Viega. "24 Deadly Sins of Software Security". "Sin 19: Use of Weak Password-Based Systems." Page
279. McGraw-Hill. 2010.
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.
Description
