Vikunja is an open-source self-hosted task management platform. Prior to version 2.2.0, the Caldav endpoint allows login using Basic Authentication, which in turn allows users to bypass the TOTP on 2FA-enabled accounts. The user can then access standard project information that would normally be protected behind 2FA (if enabled), such as project name, description, etc. Version 2.2.0 patches the issue.

Affected: Go: code.vikunja.io/api

### Summary The Caldav endpoint allows login using Basic Authentication, which in turn allows users to bypass the TOTP on 2FA-enabled accounts. The user can then access standard project information that would normally be protected behind 2FA (if enabled), such as project name, description, etc.

### Details The two files below show that when a user is accessing Caldav via Basic Authentication, it skips all steps involving 2FA. The order of operations is essentially: 1. Retrieve basic credentials. 2. Verify username. 3. Verify password. 4. Success

**pkg/routes/caldav/auth.go:45** ```go u, err := checkUserCaldavTokens(s, credentials) if user.IsErrUserDoesNotExist(err) { return false, nil } if u == nil { u, err = user.CheckUserCredentials(s, credentials) if err != nil { log.Errorf("Error during basic auth for caldav: %v", err) return false, nil } } ```

**pkg/user/user.go:358** ```go func CheckUserCredentials(s *xorm.Session, u *Login) (*User, error) { // Check if we have any credentials if u.Password == "" || u.Username == "" { return nil, ErrNoUsernamePassword{} }

// Check if the user exists user, err := getUserByUsernameOrEmail(s, u.Username) if err != nil { // hashing the password takes a long time, so we hash something to not make it clear if the username was wrong _, _ = bcrypt.GenerateFromPassword([]byte(u.Username), 14) return nil, ErrWrongUsernameOrPassword{} }

if user.Issuer != IssuerLocal { return user, &ErrAccountIsNotLocal{Use…