Arbitrary File Upload in plank/laravel-mediable Enables RCE

Executive Summary

The vulnerability exists in the plank/laravel-mediable package through version 6.4.0. It allows a remote attacker to upload a dangerous file type by exploiting the application's acceptance or preference for a client-supplied MIME type during file upload handling.

Specifically, an attacker can submit a file containing executable PHP code while declaring a benign image MIME type. If the application stores this uploaded file in a web-accessible and executable location, it can lead to arbitrary file upload and potentially remote code execution.

At the time of the vulnerability's publication, no patch was available and the vendor had not responded to coordinated disclosure attempts.

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Detection Guidance

This vulnerability involves the upload of a dangerous file type disguised with a benign image MIME type, potentially allowing arbitrary PHP code execution if stored in a web-accessible and executable location.

To detect this vulnerability on your system, you should look for uploaded files that have image MIME types but contain executable PHP code.

• Use file inspection commands to verify MIME types and file contents, for example:
• Run `file --mime-type <uploaded_file>` to check the MIME type of suspicious files.
• Use `grep -r '<?php' <upload_directory>` to search for PHP code inside uploaded files.
• Check web server logs for unusual file upload activity or access to suspicious files.
• Monitor network traffic for uploads with mismatched MIME types or unexpected file extensions.

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Impact Analysis

This vulnerability can have severe impacts including allowing an attacker to execute arbitrary code on your server remotely.

If exploited, it can lead to unauthorized control over the affected system, data breaches, service disruption, and potential further exploitation within your environment.

The high CVSS scores (up to 10.0 in version 2.0) reflect the critical nature of this vulnerability, indicating it is easy to exploit and can cause complete compromise of confidentiality, integrity, and availability.

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Compliance Impact

The vulnerability allows an attacker to upload executable PHP code by bypassing MIME type checks, potentially leading to remote code execution if the file is stored in a web-accessible and executable location.

Such a vulnerability can compromise the confidentiality, integrity, and availability of data handled by the affected application.

This may impact compliance with common standards and regulations like GDPR and HIPAA, which require protection of sensitive data and secure handling of personal information.

Specifically, unauthorized code execution could lead to data breaches or unauthorized access to personal data, violating regulatory requirements for data protection and security controls.

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Mitigation Strategies

Immediate mitigation steps include:

• Disable or avoid accepting client-supplied MIME types during file upload handling.
• Implement strict server-side validation of uploaded files by verifying both MIME type and file content.
• Restrict upload directories to non-executable locations to prevent execution of uploaded files.
• Apply file extension whitelisting and reject files with potentially dangerous extensions.
• Monitor and audit file uploads regularly for suspicious files.
• Stay updated on vendor responses or patches; at the time of publication, no patch was available.

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