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 victim's 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 victim's account password due to the username collision.

An issue in the validateemail function in CTFd/utils/validators/init.py of CTFd 3.7.3 allows attackers to cause a Regular expression Denial of Service (ReDoS) via supplying a crafted string as e-mail address during registration.

A zip slip vulnerability in the Admin import functionality of CTFd v3.8.1-18-gdb5a18c4 allows attackers to write arbitrary files outside the intended directories via supplying a crafted import.

In RedpwnCTF before version 2.3, there is a session fixation vulnerability in exploitable through the #token=$ssid hash when making a request to the /verify endpoint. An attacker team could potentially steal flags by, for example, exploiting a stored XSS payload in a CTF challenge so that victim teams who solve the challenge are unknowingly (and against their will) signed into the attacker team's account. Then, the attacker can gain points / value off the backs of the victims. This is patched in version 2.3.

Tokens in CTFd used for account activation and password resetting can be used interchangeably for these operations. When used, they are sent to the server as a GET parameter and they are not single use, which means, that during token expiration time an on-path attacker might reuse such a token to change user's password and take over the account. Moreover, the tokens also include base64 encoded user email.

This issue impacts releases up to 3.7.4 and was addressed by pull request 2679 https://github.com/CTFd/CTFd/pull/2679  included in 3.7.5 release.

A Host header injection vulnerability exists in CTFd 3.7.5, due to the application failing to properly validate or sanitize the Host header. An attacker can manipulate the Host header in HTTP requests, which may lead to phishing attacks, reset password, or cache poisoning. NOTE: the Supplier's position is that the end user is supposed to edit the NGINX configuration template to set servername (with this setting, Host header injection cannot occur).

While assignment of a user to a team (bracket) in CTFd should be possible only once, at the registration, a flaw in logic implementation allows an authenticated user to reset it's bracket and then pick a new one, joining another team while a competition is already ongoing. This issue impacts releases from 3.7.0 up to 3.7.4 and was addressed by pull request 2636 https://github.com/CTFd/CTFd/pull/2636  included in 3.7.5 release.

Lack of access control in ChallengeSolves (/api/v1/challenges/<challenge id>/solves) of CTFd v2.0.0 - v3.7.2 allows authenticated users to retrieve a list of users who have solved the challenge, regardless of the Account Visibility settings. The issue is fixed in v3.7.3+.

A vulnerability has been found in CTFd up to 3.8.4. The affected element is the function issafeurl of the file CTFd/utils/validators/init.py. Such manipulation of the argument Next leads to open redirect. The attack can be launched remotely. The exploit has been disclosed to the public and may be used. The name of the patch is 5d8515842fd1ab2c3a9f2dde9ffca907aa334ea9. Upgrading the affected component is recommended.