CVE-2006-7087 in Dotdeb PHP
Summary
by MITRE
CRLF injection vulnerability in the mail function in Dotdeb PHP before 5.2.0 Rev 3 allows remote attackers to bypass the protection scheme and inject arbitrary email headers via CRLF sequences in the query string, which is processed via the PHP_SELF variable.
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Analysis
by VulDB Data Team • 10/10/2017
The vulnerability described in CVE-2006-7087 represents a critical cross-site scripting and email header injection flaw affecting Dotdeb PHP versions prior to 5.2.0 Rev 3. This issue stems from improper input validation within the mail function where CRLF (Carriage Return Line Feed) sequences are not adequately sanitized. The vulnerability specifically exploits the PHP_SELF variable which contains the script name and query string information from HTTP requests. When attackers manipulate the query string to include CRLF characters, these sequences can be processed and injected into email headers, effectively bypassing existing security protections designed to prevent header manipulation. The flaw operates at the application layer and demonstrates a classic weakness in input sanitization where developers fail to properly validate and escape user-supplied data before incorporating it into email headers.
The technical exploitation of this vulnerability occurs when a web application using PHP processes user input through the mail function without proper sanitization of the PHP_SELF variable. When CRLF sequences are present in the query string, they are interpreted by the mail function as legitimate header terminators, allowing attackers to inject additional email headers such as From, To, CC, BCC, or even custom headers. This enables malicious actors to redirect emails, forge sender addresses, or inject arbitrary content into email messages. The vulnerability specifically targets the mail function's handling of headers where the PHP_SELF variable is processed, making it particularly dangerous in web applications that send automated emails based on user input. The flaw represents a direct violation of input validation principles and demonstrates how improper sanitization can lead to serious security consequences.
The operational impact of CVE-2006-7087 extends beyond simple header injection, potentially enabling more sophisticated attacks such as email spoofing, spam relay, and phishing campaigns. Attackers can exploit this vulnerability to send emails that appear to originate from legitimate sources, undermining trust in email communications and potentially facilitating social engineering attacks. The vulnerability also poses risks to email server configurations and can be used to bypass email filtering systems that rely on header validation. Organizations using affected PHP versions face significant exposure to reputation damage, regulatory compliance issues, and potential legal consequences from email abuse. This vulnerability aligns with CWE-1107, which specifically addresses the issue of improper neutralization of CRLF sequences, and represents a variant of the broader category of header injection attacks that fall under ATT&CK technique T1190 for "Exploit Public-Facing Application" and T1566 for "Phishing" through email manipulation.
Mitigation strategies for CVE-2006-7087 require immediate patching of affected PHP installations to version 5.2.0 Rev 3 or later where the vulnerability has been addressed. Organizations should implement comprehensive input validation and sanitization measures, particularly for variables that will be used in email headers. The recommended approach includes proper escaping of CRLF sequences, validation of user input, and implementation of strict header sanitization routines. Developers should avoid using user-supplied data directly in email headers and instead implement proper data validation frameworks. Additional protective measures include monitoring email logs for unusual header patterns, implementing email authentication mechanisms such as SPF, DKIM, and DMARC, and establishing robust input filtering at multiple layers of the application architecture. The vulnerability serves as a critical reminder of the importance of secure coding practices and proper input validation in preventing header injection attacks that can compromise email security and overall system integrity.