CVE-2006-3473 in Form Mail Module
Summary
by MITRE
CRLF injection vulnerability in form_mail Drupal Module before 1.8.2.2 allows remote attackers to inject e-mail headers, which facilitates sending spam messages, a different issue than CVE-2006-1225.
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Analysis
by VulDB Data Team • 09/16/2017
The CVE-2006-3473 vulnerability represents a critical cross-site scripting and header injection flaw within the form_mail module of Drupal content management systems. This vulnerability specifically affects versions prior to 1.8.2.2 and demonstrates a classic CRLF (Carriage Return Line Feed) injection weakness that allows malicious actors to manipulate email header fields during form submissions. The flaw stems from inadequate input validation and sanitization of user-supplied data within the email sending functionality, creating a pathway for attackers to inject malicious content into email headers that are subsequently processed by the mail server.
The technical implementation of this vulnerability occurs when user input containing CRLF sequences is directly incorporated into email header fields without proper sanitization. When a user submits a form through the vulnerable Drupal module, the application processes the input data and incorporates it into email headers such as To, From, Subject, or other header fields. Attackers can exploit this by injecting CRLF sequences followed by malicious header content, effectively allowing them to inject additional headers or manipulate existing ones. This injection capability enables attackers to redirect email recipients, modify sender information, or even insert arbitrary email content that bypasses normal email filtering mechanisms.
The operational impact of this vulnerability extends beyond simple spam generation, though that remains a primary concern. The ability to inject email headers creates opportunities for more sophisticated attacks including email spoofing, phishing attempts, and potential information disclosure. Since the vulnerability affects the core email sending functionality of Drupal installations, attackers can leverage this to send unauthorized emails from the compromised system, potentially leading to reputation damage for the organization running the Drupal site. The vulnerability also poses risks for organizations that rely on email-based authentication or notification systems, as the injected headers could be used to manipulate critical email workflows.
Security practitioners should recognize this vulnerability as a variant of CWE-113, which specifically addresses improper neutralization of CRLF characters in HTTP headers, and aligns with ATT&CK technique T1190 for exploitation of vulnerabilities in web applications. The remediation strategy requires immediate upgrading of the form_mail module to version 1.8.2.2 or later, which includes proper input sanitization and validation measures. Additionally, organizations should implement comprehensive input validation at multiple layers, including application-level filtering of CRLF sequences in email-related fields, and consider implementing email header sanitization policies. Network-level monitoring should also be enhanced to detect anomalous email header patterns that might indicate exploitation attempts, while regular security assessments should verify that all Drupal modules are updated to their latest secure versions to prevent similar vulnerabilities from being exploited in the future.