Executive Summary

CVE-2021-47830 is a Cross-Site Request Forgery (CSRF) vulnerability in the GetSimple CMS My SMTP Contact Plugin version 1.1.1. An attacker can craft a malicious webpage that, when visited by an authenticated administrator, can change the SMTP configuration settings of the plugin without authorization. This vulnerability arises because the plugin lacks proper CSRF protection tokens on its configuration form, allowing unauthorized POST requests to be submitted. Although this vulnerability alone does not directly enable remote code execution, it allows unauthorized changes to SMTP settings. However, when combined with other flaws (such as PHP code injection in the plugin), it can lead to remote code execution and full server compromise in later versions. [2, 4]

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Impact Analysis

This vulnerability can allow an attacker to make unauthorized changes to the SMTP configuration settings of the GetSimple CMS My SMTP Contact Plugin if an authenticated administrator visits a malicious webpage. While the CSRF vulnerability alone does not directly enable remote code execution, it can be exploited in combination with other vulnerabilities (such as PHP code injection) to achieve remote code execution on the hosting server. This can lead to full compromise of the server, allowing attackers to execute arbitrary PHP code, upload webshells, and control the server remotely. [2, 4]

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Detection Guidance

Detection of this vulnerability involves monitoring for unauthorized changes to the SMTP configuration settings of the My SMTP Contact Plugin in GetSimple CMS, especially POST requests to the plugin's configuration endpoint originating from an authenticated administrator's session. Since the vulnerability exploits CSRF, look for unusual POST requests without proper CSRF tokens. Additionally, check for unexpected files such as webshell.php on the server, which may indicate exploitation. Commands to assist detection could include: 1) Using web server logs to search for POST requests to the plugin endpoint, e.g., `grep 'POST /path/to/plugin/config' /var/log/apache2/access.log`; 2) Searching for suspicious files like `find /var/www/html/ -name 'webshell.php'`; 3) Monitoring for unexpected changes in plugin configuration files or timestamps with `stat` or `ls -ltr` commands; 4) Using intrusion detection systems or web application firewalls to detect CSRF attack patterns. However, no specific detection commands are provided in the resources. [3, 4]

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Mitigation Strategies

Immediate mitigation steps include: 1) Updating the My SMTP Contact Plugin to version 1.1.2 or later, which implements CSRF nonce tokens and fixes the vulnerabilities; 2) Restricting administrative access to trusted users only; 3) Implementing proper input sanitization beyond `htmlspecialchars()` to prevent code injection; 4) Enforcing CSRF protections and validating user inputs properly; 5) Monitoring for unauthorized file modifications and removing any uploaded webshells; 6) Configuring session cookies with the SameSite flag to reduce CSRF risk; 7) Harden server security and consider using web application firewalls to block malicious requests. These steps help prevent exploitation of the CSRF and PHP code injection vulnerabilities described. [3, 4]

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