Compliance Impact

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Impact Analysis

This vulnerability can have severe impacts including unauthorized remote code execution on the affected server. An attacker can gain control over the system by executing arbitrary system commands, potentially leading to data theft, server compromise, or further attacks within the network.

Because the exploit requires no authentication or user interaction, it poses a high risk of exploitation, making affected systems highly vulnerable to attackers.

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Executive Summary

CVE-2020-37186 is a critical remote code execution vulnerability in Chevereto Core version 3.13.4 and earlier. It occurs during the database configuration installation process, where an attacker can manipulate the database table prefix parameter to inject malicious PHP code.

This injection allows the attacker to write a PHP shell file on the server, which can then be used to execute arbitrary system commands remotely via a specially crafted POST request. The vulnerability requires no privileges, user interaction, or authentication and can be exploited over the network.

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Detection Guidance

[{'type': 'paragraph', 'content': 'This vulnerability can be detected by monitoring for unusual POST requests to the installation endpoint (/install) that include manipulation of the database table prefix parameter with injected PHP code.'}, {'type': 'paragraph', 'content': 'Specifically, detection involves looking for POST requests containing suspicious payloads that attempt to write PHP shell code via the db_table_prefix parameter.'}, {'type': 'paragraph', 'content': 'One approach is to inspect web server logs for POST requests to /install with unusual or encoded parameters.'}, {'type': 'paragraph', 'content': 'Example commands to detect such activity might include:'}, {'type': 'list_item', 'content': "Using grep to find suspicious POST requests in Apache logs: grep -i 'POST /install' /var/log/apache2/access.log | grep 'db_table_prefix'"}, {'type': 'list_item', 'content': 'Using network monitoring tools like tcpdump or Wireshark to capture HTTP POST requests to the installation endpoint and analyze payloads for PHP code injection patterns.'}, {'type': 'list_item', 'content': "Searching for newly created or modified PHP files in the web root that could be malicious shells: find /var/www/html -name '*.php' -mtime -7"}, {'type': 'paragraph', 'content': "Automated detection can also be implemented by scanning for the presence of PHP files containing the injected code pattern that checks for the POST parameter 'ccc' and executes system commands."}] [2, 3]

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Mitigation Strategies

Immediate mitigation steps include:

• Avoid using vulnerable versions of Chevereto Core (3.13.4 and earlier) and upgrade to a fixed version if available.
• Restrict access to the installation endpoint (/install) to trusted administrators only, or disable it after installation.
• Implement web application firewall (WAF) rules to block POST requests containing suspicious payloads targeting the db_table_prefix parameter.
• Harden PHP execution permissions in upload directories and restrict HTTP methods to GET where possible, as done in later Chevereto releases.
• Monitor logs for suspicious activity and remove any unauthorized PHP shell files found on the server.

These steps help prevent exploitation by limiting the attack surface and blocking malicious payloads.

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