> For the complete documentation index, see [llms.txt](https://0xn3va.gitbook.io/application-security-handbook/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://0xn3va.gitbook.io/application-security-handbook/web-application/authentication/password-reset.md).
# Password Reset
## Overview
This page contains recommendations for the implementation of password reset functionality.
## General
* Implement a password reset in one of the following ways:
* [Password reset based on a URL token](#password-reset-based-on-a-url-token)
* [Password reset based on a one-time password](#password-reset-based-on-a-one-time-password)
* During password reset do **not** indicate if a user with entered data exists or not. Ask for a username/email address/phone number/etc. and inform the a that if there is a user with the data entered, reset recommendations will be sent to them via the appropriate communication channel.
* Only block an old password after a user has successfully passed the password reset step.
* Do **not** automatically sign a user in. Once a user sets their new password, log out a user and send them to a usual login mechanism (with multi-factor authentication, if enabled).
* Terminate all active sessions after the password reset. You can explicitly ask a user if they want to invalidate all of their existing sessions.
* During password reset, request at least the following data:
* New password.
* Confirmation of the new password.
* Link a random token (or one-time password) to an individual user in a database.
* Do **not** reveal a current password in any way during the password reset.
* Do **not** reveal a random token (or one-time password) in any way during the password reset.
* Log successful and failed password reset attempts, see the [Logging and Monitoring](/application-security-handbook/web-application/logging-and-monitoring.md) page.
* Comply with requirements from the [Error and Exception Handling](/application-security-handbook/web-application/error-and-exception-handling.md) page.
* Implement a password reset in the following way:
* [Password reset based on a time-based one-time password](#password-reset-based-on-a-time-based-one-time-password)
## Password reset based on a URL token
* Send a password reset URL to a user and pass a random token in the query string of the URL. For example:
```
https://website.local/account/password/reset?token=GiOzXAwlZ17NsW4CkVV8MQXtiQN9cWiY
```
* Generate a random token using a cryptographically strong random generator, see the [Cryptography: Random Generators](/application-security-handbook/web-application/cryptography/random-generators.md) page.
* Use random tokens of length 32+ bytes.
* Set a short expiration time for a random token (\~ 24 hours).
* Use a random token once. Delete a random token or transfer it to a final status that prohibits reusing.
* Do **not** rely on the `Host` HTTP header while creating the reset URLs to avoid the [Host Header Injection](https://owasp.org/www-project-web-security-testing-guide/stable/4-Web_Application_Security_Testing/07-Input_Validation_Testing/17-Testing_for_Host_Header_Injection) attack. Either hardcode the URL or validate against a list of trusted domains using an allow list.
* Add the [Referrer-Policy](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Referrer-Policy) HTTP header with the `noreferrer` value to the reset password page in order to avoid [referrer leakage](https://portswigger.net/kb/issues/00500400_cross-domain-referer-leakage).
## Password reset based on a one-time password
* Send a one-time password to a user for confirmation of the password reset.
* Comply with the requirements from the [Authentication: One Time Password (OTP)](/application-security-handbook/web-application/authentication/one-time-password-otp.md) page.
## Password reset based on a time-based one-time password
* Use a time-based one-time password generated on the user side for confirmation of the password reset.
* Comply with the requirements from the [Authentication: One Time Password (OTP)](/application-security-handbook/web-application/authentication/one-time-password-otp.md) page.
## References
* [OWASP Cheat Sheet Series: Forgot Password Cheat Sheet](https://cheatsheetseries.owasp.org/cheatsheets/Forgot_Password_Cheat_Sheet.html)
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