CVE-2006-4505 in NX5Linx
Summary
by MITRE
CRLF injection vulnerability in links.php in NX5Linx 1.0 allows remote attackers to inject arbitrary HTTP headers and conduct HTTP response splitting attacks via a CRLF sequence in the url parameter.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 08/03/2018
The CVE-2006-4505 vulnerability represents a critical cross-site scripting and response splitting flaw within the NX5Linx 1.0 web application framework. This vulnerability specifically affects the links.php component where user input is not properly sanitized before being incorporated into HTTP response headers. The flaw stems from insufficient validation of the url parameter which accepts arbitrary CRLF (Carriage Return Line Feed) sequences that can be embedded within HTTP headers, enabling attackers to manipulate the HTTP response structure. Such injection capabilities fundamentally compromise the integrity of web server responses and create opportunities for sophisticated attack vectors.
The technical exploitation of this vulnerability occurs through the manipulation of HTTP headers via CRLF sequences that are typically represented as %0d%0a in URL-encoded format. When an attacker submits a malicious url parameter containing these sequences, the application processes the input without proper sanitization, allowing the injected headers to be appended to the HTTP response. This creates a condition where attackers can inject additional HTTP headers, potentially including Set-Cookie directives, Content-Type modifications, or other header fields that can alter the browser's interpretation of the response. The vulnerability is classified under CWE-113 as "Improper Neutralization of CRLF Sequences in HTTP Headers ('CRLF Injection')", which is a well-documented weakness in web application security that has been consistently identified across numerous frameworks and applications.
The operational impact of this vulnerability extends beyond simple header injection, as it enables HTTP response splitting attacks that can lead to session hijacking, cache poisoning, and cross-site scripting exploitation. When an attacker successfully injects headers, they can manipulate browser behavior by injecting malicious cookies or redirecting responses to attacker-controlled content. The vulnerability is particularly dangerous because it allows for the creation of multiple HTTP responses within a single HTTP transaction, enabling attackers to craft responses that appear legitimate to the victim's browser while actually delivering malicious content. This characteristic makes the vulnerability particularly effective for phishing attacks, session fixation, and other sophisticated web-based attacks that rely on manipulating HTTP communication channels.
Security professionals should implement comprehensive input validation and sanitization measures to prevent CRLF injection attacks in web applications. The recommended mitigations include implementing strict validation of all user-supplied input before it is incorporated into HTTP headers or response content, using proper encoding techniques such as URL encoding or HTML entity encoding, and implementing Content Security Policy headers to limit the impact of potential injection attacks. Organizations should also consider implementing web application firewalls that can detect and block known CRLF injection patterns, and establish secure coding practices that emphasize proper input validation and output encoding. This vulnerability aligns with ATT&CK technique T1190 "Exploit Public-Facing Application" and demonstrates the importance of addressing HTTP header injection vulnerabilities as part of comprehensive web application security programs. The vulnerability serves as a reminder of the critical need for secure coding practices and proper input sanitization to prevent attackers from manipulating HTTP communication protocols and compromising web application integrity.