Source: cve@mitre.org
The setFrom function in the Sendmail adapter in the zend-mail component before 2.4.11, 2.5.x, 2.6.x, and 2.7.x before 2.7.2, and Zend Framework before 2.4.11 might allow remote attackers to pass extra parameters to the mail command and consequently execute arbitrary code via a \" (backslash double quote) in a crafted e-mail address.
Critical vulnerability in Zend Framework's mail component allows for remote code execution (RCE). By crafting a malicious email address containing a backslash-double quote sequence, attackers can inject arbitrary commands into the mail command, potentially leading to complete system compromise and data exfiltration.
Step 1: Payload Delivery: The attacker crafts a malicious email address containing a backslash-double quote sequence (\") followed by the desired command and arguments (e.g., attacker@example.com \" -oQ/tmp/ -X/var/www/html/shell.php).
Step 2: Injection Point: The crafted email address is submitted to a web application using the vulnerable Zend Framework mail component.
Step 3: Vulnerable Function Call: The application calls the setFrom function in the Sendmail adapter, passing the malicious email address as input.
Step 4: Command Execution: The setFrom function, due to the lack of proper sanitization, passes the attacker-controlled email address directly to the mail command. The backslash-double quote sequence allows the attacker to inject arbitrary command-line arguments.
Step 5: Code Execution: The injected command is executed by the system, allowing the attacker to execute arbitrary code, such as uploading a web shell or gaining remote access.
The vulnerability stems from insufficient input validation within the setFrom function of the Sendmail adapter in Zend Framework's mail component. Specifically, the code fails to properly sanitize the email address provided by the user before passing it to the mail command. The backslash-double quote sequence (\") is used to escape the double quote character, allowing attackers to inject arbitrary command-line arguments. This bypasses security checks and allows for the execution of malicious code. The root cause is a lack of proper input validation and command injection vulnerability.
While no specific APT groups are definitively linked, the ease of exploitation makes this a likely target for a wide range of attackers, including those seeking initial access or data exfiltration. Not currently listed on CISA KEV, but the severity and ease of exploitation warrant close monitoring.
Network traffic analysis: Monitor for unusual email traffic patterns, especially those containing suspicious characters in the 'From' or 'Reply-To' headers.
File system monitoring: Look for unexpected file creations or modifications in web server directories (e.g., /var/www/html/) or other sensitive locations.
Log analysis: Examine mail server logs and application logs for suspicious activity, such as command injection attempts or errors related to email processing.
Intrusion Detection System (IDS) rules: Implement IDS rules to detect the backslash-double quote sequence or other malicious payloads in email headers.
Web Application Firewall (WAF) rules: Configure WAF rules to block requests containing the malicious payload.
Upgrade to a patched version of Zend Framework (2.4.11, 2.5.x, 2.6.x, or 2.7.2 or later).
Implement robust input validation to sanitize all user-supplied email addresses before passing them to the mail command. This includes escaping special characters and validating the email address format.
Use a secure email sending method that does not rely on direct command execution. Consider using a dedicated email sending library or service that handles sanitization and security.
Apply the principle of least privilege: Ensure that the web server user has minimal permissions to prevent attackers from escalating privileges.
Regularly update all software and dependencies to patch known vulnerabilities.
Implement a Web Application Firewall (WAF) to filter malicious requests.