if (preg_match('/[\x00-\x1F\x7F]/', $input)) http_response_code(400); exit("Invalid characters");
If you're using a vulnerable version of the script, take immediate action to update or patch your installation to prevent exploitation. php email form validation - v3.1 exploit
The most significant and relevant finding is the series of vulnerabilities (CVE-2016-10033 and CVE-2016-10045), which affected virtually all PHP contact forms using outdated versions of the PHPMailer library. Remote Execution Here's an example of an exploit:
(queue directory), an attacker can force the server to write a new PHP file (a "webshell") into the web root directory. Remote Execution php email form validation - v3.1 exploit
Here's an example of an exploit:
When the PHP mail() function processes this input, it interprets the \r\n sequence as a command to start a new line. The resulting email headers are reconstructed as: From: user@example.com Bcc: victim1@target.com Bcc: victim2@target.com
If the script simply concatenates the user input into the header string, an attacker can input the following: user@example.com\r\nBcc: victim1@target.com\r\nBcc: victim2@target.com