CVE-2012-0796 in Moodle
Summary
by MITRE
class.phpmailer.php in the PHPMailer library, as used in Moodle 1.9.x before 1.9.16, 2.0.x before 2.0.7, 2.1.x before 2.1.4, and 2.2.x before 2.2.1 and other products, allows remote authenticated users to inject arbitrary e-mail headers via vectors involving a crafted (1) From: or (2) Sender: header.
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Analysis
by VulDB Data Team • 12/06/2021
The vulnerability identified as CVE-2012-0796 represents a critical email header injection flaw within the PHPMailer library, which serves as a foundational component for email functionality in numerous web applications including Moodle and other platforms. This security weakness stems from inadequate input validation and sanitization mechanisms within the class.phpmailer.php file, specifically when processing email header fields. The vulnerability affects multiple versions of Moodle and other software products that rely on PHPMailer for email transmission, creating widespread exposure across various web applications. The flaw enables authenticated attackers to manipulate email headers by crafting malicious input that gets processed without proper sanitization, potentially leading to severe consequences including email spoofing, spam relay, and unauthorized message delivery.
The technical exploitation of this vulnerability occurs through manipulation of the From: or Sender: header fields in email messages. When an attacker with valid authentication credentials submits a crafted email header containing malicious content, the PHPMailer library fails to properly validate or escape the input before incorporating it into the email transmission process. This allows attackers to inject additional email headers or modify existing ones, potentially enabling them to bypass email security measures, redirect messages to unintended recipients, or forge sender information. The vulnerability specifically targets the header injection mechanism where user-supplied data is directly concatenated into email headers without appropriate sanitization, creating a pathway for attackers to execute header injection attacks. This flaw aligns with CWE-94, which describes improper validation of dangerous or unexpected data, and represents a classic example of insecure input handling in email processing components.
The operational impact of CVE-2012-0796 extends beyond simple header manipulation, potentially enabling sophisticated attack vectors that can compromise email systems and user trust. Attackers can exploit this vulnerability to send spam messages through compromised systems, relay malicious emails, or perform phishing attacks by forging sender identities. The authenticated nature of the attack means that only users with legitimate access credentials need to be compromised, making the vulnerability particularly dangerous in environments where user access is not properly controlled. Organizations using affected versions of Moodle or other vulnerable software face significant risks including reputation damage, compliance violations, and potential legal consequences due to unauthorized email activities. The attack can be executed through normal email submission processes, making detection difficult and allowing attackers to remain undetected while conducting malicious activities through the compromised email infrastructure.
Mitigation strategies for this vulnerability require immediate patching of affected software versions, with the most effective solution being the upgrade to PHPMailer versions that properly sanitize email headers. Organizations should implement comprehensive input validation measures that filter or escape special characters in email header fields, particularly those that could enable header injection attacks. Network monitoring and email security solutions should be enhanced to detect unusual header patterns or unauthorized email activities that might indicate exploitation attempts. Security teams should also review and strengthen authentication mechanisms to minimize the risk of credential compromise, as the vulnerability requires authenticated access to exploit. Additionally, implementing email header sanitization at multiple layers including application code, web server configurations, and email gateway systems can provide defense-in-depth protection against similar vulnerabilities. The remediation process should include thorough testing of patched versions to ensure that legitimate email functionality remains intact while addressing the security flaw. Organizations should also consider implementing email logging and audit trails to track email header modifications and detect potential exploitation attempts. This vulnerability highlights the importance of proper input validation in email systems and demonstrates how seemingly minor security flaws can have significant operational impacts on email infrastructure security.