Incorrect username validation in the registration process of CTFd v2.0.0 - v2.2.2 allows an attacker to take over an arbitrary account if the username is known and emails are enabled on the CTFd instance. To exploit the vulnerability, one must register with a username identical to the victims username, but with white space inserted before and/or after the username. This will register the account with the same username as the victim. After initiating a password reset for the new account, CTFd will reset the victims account password due to the username collision.
The product contains a mechanism for users to recover or change their passwords without knowing the original password, but the mechanism is weak.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Ctfd | Ctfd | 2.0.0 (including) | 2.2.2 (including) |
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. Weak password recovery schemes completely undermine a strong password authentication scheme. This weakness may be that the security question is too easy to guess or find an answer to (e.g. because the question is too common, or the answers can be found using social media). 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.