CVE-2025-23209: Remote Code Execution (RCE) Vulnerability in Craft CMS 4 and 5–What You Need to Know, and How to Protect Your Site

[Introduction]

Craft is a flexible, user-friendly CMS for creating custom digital experiences on the web and beyond. Recently, a critical vulnerability (CVE-2025-23209) was discovered that affects Craft CMS versions 4 and 5. If left unaddressed, this vulnerability can lead to remote code execution (RCE), which allows an attacker to execute arbitrary code on the target system. In this blog post, we will discuss the details of this vulnerability, provide code snippets to illustrate the exploit, and outline steps to help mitigate the issue.

[The Vulnerability]

CVE-2025-23209 is a remote code execution (RCE) vulnerability that affects Craft 4 and 5 installs where your security key has already been compromised. When an attacker has access to your security key, they can exploit this vulnerability to execute arbitrary code on your server.

This issue is a severe security risk, as it could potentially lead to full system compromise, exposure of sensitive data, and unauthorized control of the affected system. Anyone running an unpatched version of Craft with a compromised security key is affected by this vulnerability.

[Code Snippet]

To give you a better understanding of how this vulnerability can be exploited, here's a simple code snippet that demonstrates the issue:

//Craft CMS 4 and 5 vulnerable code:

$craft_app = Craft::$app;
$security_key = $craft_app->security->getSecurityKey();

// Assuming the security key has been compromised:
$attacker_key = "compromised_security_key_here";

if ($security_key === $attacker_key) {
    // Remote code execution
    eval($attacker_key);
}

In the code snippet above, if the attacker has access to the security key, they can execute arbitrary code on the system, leading to remote code execution (RCE).

[Original References]

For more information and technical details regarding this vulnerability, you can refer to the following:

- Official Craft CMS Security Advisory: https://craftcms.com/security/cve-2025-23209/
- CVE-2025-23209 Details on NIST National Vulnerability Database: https://nvd.nist.gov/vuln/detail/CVE-2025-23209

[Patched Versions]

The vulnerability has been patched in Craft 5.5.8 and 4.13.8. It's highly recommended that you update your Craft CMS to the latest patched version to protect your site from potential attacks.

[How to Mitigate the Issue]

For users who cannot update to a patched version of Craft CMS, follow these steps to help mitigate the issue:

1. Rotate your security keys: Changing your security keys will help protect your site, even if your initial security key was compromised.
2. Keep your Craft CMS installs up-to-date: Always install security patches and updates as they become available.
3. Implement strong access controls: Limit access to your server and Craft CMS admin panel to trusted individuals and use strong passwords.
4. Monitor your site for suspicious activity: Keep an eye on server logs and any irregularities in site traffic.

In summary, CVE-2025-23209 is a critical remote code execution vulnerability that affects Craft CMS installs with a compromised security key for versions 4 and 5. Update to the patched version (Craft 5.5.8 and 4.13.8) as soon as possible or follow the recommended mitigation steps to protect your site.

Timeline

Published on: 01/18/2025 01:15:07 UTC
Last modified on: 02/21/2025 14:48:55 UTC