CVE-2023-22621: SSTI to RCE in the Users-Permissions Plugin

Summary of CVE-2023-22621 Vulnerability Details

• CVE: CVE-2023-22621
• CVSS v3.1 Vector: AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
• Affected Versions: <=4.5.5
• How to Patch: Immediately update your Strapi to version >=4.5.6! If you using Strapi 3.x.x or below, IMMEDIATELY UPDATE TO A PATCHED 4.x.x VERSION! Strapi versions 3.x.x reached its end of life support on the December 31st 2022, and will no longer receive security updates. If you are unable to upgrade to a patched version, please see the following repository for patch-package patches.

Description of CVE-2023-22621

On December 29th, 2022, the security researcher reported to us an SSTI (server-side template injection) vulnerability impacting our users-permission plugin’s email template system. Please note the users-permissions plugin is installed by default. This SSTI vulnerability made it possible to modify the email template to execute malicious code via RCE (remote code execution). This vulnerability’s scope was originally believed to be exploitable only if a malicious actor had access to the Strapi Admin Panel. On January 4th 2022, a CVE was submitted in a draft state with the following ID: CVE-2023-22621.

While we won’t go into the deep details of this vulnerability (please see the related blog post by the security researcher who reported the vulnerability to us) we did want to communicate on the IoC’s (indicators of compromise) so that our users are able to review their application logs to detect if they were impacted. Do note that this vulnerability impacts all known Strapi v3 and Strapi v4 versions prior to v4.5.6. If you have not already upgraded beyond Strapi v4.5.6 we do urge you to do so as quickly as possible (we strongly advise upgrading beyond v4.8.0 where other security vulnerabilities were patched). If you are unable to upgrade we have released several patch-package patches for this particular vulnerability.

CVE-2023-22621 IoC’s

Using just the request log files, the only IoC to search for is a PUT request to URL path /users-permissions/email-templates. This IoC only indicates that a Strapi email template was modified on your server and by itself does not indicate if your Strapi server has been compromised. If this IoC is detected, you will need to manually review your email templates on your Strapi server and backups of your database to see if any of the templates contain a lodash template delimiter (eg. <%STUFF HERE%>) that contains suspicious JavaScript code. Generally speaking these templates should look like the following, you may have minor adjustments but any unrecognized code should be considered suspicious.

Reset Password Template:

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<p>We heard that you lost your password. Sorry about that!</p>

<p>But don’t worry! You can use the following link to reset your password:</p>
<p><%= URL %>?code=<%= TOKEN %></p>

<p>Thanks.</p>

Email Confirmation Template:

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<p>Thank you for registering!</p>

<p>You have to confirm your email address. Please click on the link below.</p>

<p><%= URL %>?confirmation=<%= CODE %></p>

<p>Thanks.</p>

Specifically you should look for odd code contained within the <%STUFF HERE%> blocks as this is what is used to bypass the lodash templating system. If you find any code that is not a variable name, or a variable name that is not defined in the template you are most likely impacted and should take immediate steps to confirm there are no malicious applications running on your servers.

CVE-2023-22621 Timeline

CVE-2023-22893: Authentication Bypass for AWS Cognito Login Provider

Summary of CVE-2023-22893 Vulnerability Details

• CVE: CVE-2023-22893
• CVSS v3.1 Vector: AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N
• Impacted Versions: >=3.2.1,<4.6.0
• How to Patch: Immediately update your Strapi to version >=4.6.0! If you using Strapi 3.x.x or below, IMMEDIATELY UPDATE TO A PATCHED 4.x.x VERSION! Strapi versions 3.x.x reached its end of life support on the December 31st 2022, and would not receive a patch for this vulnerability!

Description of CVE-2023-22893

On January 1st, 2023, the security researcher reported to us an authentication bypass specifically for the AWS Cognito authentication provider for the users-permissions plugin. This vulnerability made it possible for any user to authenticate against a Strapi application using this authentication provider by spoofing the JWT token using a valid victims email address as the contents of the JWT were not properly verified against AWS. This vulnerability only impacted the users-permissions plugin and not Strapi Enterprise's SSO feature as the two systems use entirely different authentication provider packages (users-permissions uses Grant/Purest whereas the Admin Panel uses Passport.js).

While we won’t go into the deep details of this vulnerability (please see the related blog post by the security researcher who reported the vulnerability to us) we did want to communicate on the IoC’s (indicators of compromise) so that our users are able to review their application logs to detect if they were impacted. Do note that this vulnerability impacts all known Strapi v3 and Strapi v4 versions prior to v4.6.0. If you have not already upgraded beyond Strapi v4.6.0 we do urge you to do so as quickly as possible (we strongly advise upgrading beyond v4.8.0 where other security vulnerabilities were patched). Again please note that if you do not currently use the AWS Cognito authentication provider you are not impacted by this vulnerability.

CVE-2023-22893 IoC’s

Reviewing of application logs is recommended to detect any suspicious activity. Running the following regex pattern will extract all ID tokens sent to /api/auth/cognito/callback

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/\/api\/auth\/cognito\/callback\?[\s\S]*id_token=\s*([\S]*)/

Once you have a list of the ID tokens, you will need to verify each token using the public key file for your AWS Cognito user pool that you can download from https://cognito-idp.{region}.amazonaws.com/{userPoolId}/.well-known/jwks.json. If there are any JWT tokens that cannot be verified using the correct public key, then you need to inspect the JWT body and see if it contains the email and cognito:username claims (example below).

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{
  "cognito:username": "auth-bypass-example",
  "email": "user@example.com"
}

If there are any JWTs that have this body, verify when the account with the email address was created. If the account was created earlier than the request to /api/auth/cognito/callback with the invalid JWT token, then you need to contact the user to inform them their account has been breached!

After upgrading to Strapi v4.6.0 or greater you will need to reconfigure your AWS Cognito provider to include the JWKS URL for it to work properly. If you do not reconfigure your provider you will receive an error message when attempting to login.

CVE-2023-22893 Timeline

CVE-2023-22894: Leaking Sensitive User Information by Filtering on Private Fields

Summary of CVE-2023-22894 Vulnerability Details

• CVE: CVE-2023-22894
• CVSS v3.1 Vector: AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Affected Versions: >=3.2.1,<4.8.0
• How to Patch: Immediately update your Strapi to version >4.8.0! If you using Strapi 3.x.x or below, IMMEDIATELY UPDATE TO A PATCHED 4.x.x VERSION! Strapi versions 3.x.x reached its end of life support on the December 31st 2022, and would not receive a patch for this vulnerability!

Description of CVE-2023-22894

CVE-2023-22894 IoC’s

The exploitation of CVE-2023-22894 is easily detectable, since the payload is within the GET parameters and are normally included in request logs. The following regex pattern will extract requests that are exploiting this vulnerability to leak user's email, password and password reset token columns.

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/(\[|%5B)\s*(email|password|reset_password_token|resetPasswordToken)\s*(\]|%5D)/

You can search log files for this IoC by using the following grep command.

grep -iE '(\[|%5B)\s*(email|password|reset_password_token|resetPasswordToken)\s*(\]|%5D)' $PATH_TO_LOG_FILE

If the above regex pattern matches any lines in your log files, take extra precaution to look out for multiple requests that include password, reset_password_token or resetPasswordToken. This would indicate that an attacker has leaked the password hashes and reset tokens on your Strapi server and you need to immediately start an incident response!

CVE-2023-22894 Timeline

Chaining of CVE-2023-22621 and CVE-2023-22894 Together to Achieve Unauthenticated RCE

Thanks to the diligent work of the security researcher it was made apparent that it was possible to combine both CVE-2023-22621 and CVE-2023-22894 which combined allow for an unauthenticated RCE on all Strapi <=4.5.5 servers. By exploiting and hijacking a super admin account via the admin panel and using that account to modify the users-permissions template it would be possible to execute arbitrary code on the server.

Exploiting CVE-2023-22894

1. Search for any entry on a publicly accessible entry for a collection that was created or updated by a super administrator user.
2. Leak the email address for the super administrator user.
3. Perform the forgot my password action for the super administrator account.
4. Leak the reset password token for the super administrator user.
5. Set a new password for the super administrator account and grab the API token for the admin API.

Exploiting CVE-2023-22621

1. Set a crafted email template that executes arbitrary terminal commands when rendered for when API accounts register.
2. Enable sending emails on API account registration.
3. Register a new API account to trigger the RCE vulnerability.
4. Arbitrary code is then executed on the targeted server.

Summary and a Thank You to the Security Researcher

We on the Strapi security team wanted to give a massive shout out to the security researcher GhostCcamm. Never in Strapi's history have we had a security researcher go above and beyond to help us improve the security of our product. We are very thankful for their work and dedication, the amount of detail they placed in their PoCs was simply outstanding and allowed us to quickly verify and patch the vulnerabilities. We simply cannot thank them enough for their work and for transparency; Strapi does not have a bug bounty program (for several reasons, largely because it tends to attract very mundane and invalid security reports) but in this case we did want to reward GhostCcamm for their work and did offer them a monetary reward.

For additional information about each of the vulnerabilities from the security researcher's perspective, please see their extremely detailed blog post, additionally below are their social links.

• Blog post for these vulnerabilities: https://www.ghostccamm.com/blog/multi_strapi_vulns/
• Twitter: https://twitter.com/GhostCcamm
• Website: https://www.ghostccamm.com
• GitHub: https://github.com/Ccamm

We cannot thank GhostCcamm enough and look forward to continuing to work with them in the future. Their patience and constant communication throughout the process was simply outstanding and we sincerely hope that others will follow your example.

Commitment to Responsible Disclosure

We at Strapi do believe in responsible disclosure, in the case of these vulnerabilities we have worked with the security researcher to ensure that the vulnerabilities were patched before the full disclosure of the vulnerabilities. Once a vulnerability is patched, we added a notice to our release notes to inform users there was a security vulnerability but initially wanted to delay detailed disclosure for a few weeks to give time for users to upgrade before release of the full disclosure. As an additional step we did immediately notify our customers via several emails beforehand to ensure they were aware of the vulnerabilities and to upgrade their Strapi servers.

We do believe that delaying the detailed disclosure in this case was important to ensure that users had the time required to upgrade their Strapi servers before making the details of each vulnerability public and thus placing that information in the hands of bad actors. We also believe that the security researcher was very professional and responsible in their handling of the vulnerabilities and we are very thankful for their work in helping us to improve the security of Strapi.

We urge anyone who believes they have discovered a security vulnerability to assist us in responsibly disclosing the vulnerability to us by emailing security@strapi.io.

Thanks,

The Strapi Security Team