CVE-2002-1405 in Lynx
Summary
by MITRE
CRLF injection vulnerability in Lynx 2.8.4 and earlier allows remote attackers to inject false HTTP headers into an HTTP request that is provided on the command line, via a URL containing encoded carriage return, line feed, and other whitespace characters.
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Analysis
by VulDB Data Team • 09/06/2025
The CVE-2002-1405 vulnerability represents a critical cross-site scripting and header injection flaw within the Lynx web browser version 2.8.4 and earlier. This vulnerability specifically targets the command-line parameter processing functionality of Lynx, where users can provide URLs directly through command-line arguments. The flaw arises from insufficient input validation and sanitization of HTTP headers within the URL parsing mechanism. Attackers can exploit this weakness by crafting malicious URLs containing encoded carriage return and line feed characters, which are typically represented as %0d%0a in URL encoding schemes. When Lynx processes these malformed URLs, it fails to properly sanitize the input, allowing attackers to inject arbitrary HTTP headers into the outgoing requests. This vulnerability is particularly dangerous because it enables man-in-the-middle attacks, session hijacking, and HTTP response splitting attacks, as the injected headers can manipulate the browser's behavior and potentially redirect traffic to malicious destinations.
The technical implementation of this vulnerability stems from the lack of proper input validation within Lynx's HTTP request construction process. When users specify a URL via command-line arguments, the browser's URL parser does not adequately filter or escape special characters including carriage return %0d, line feed %0a, and other whitespace sequences. This parsing failure creates a condition where attackers can inject additional HTTP headers that get appended to the original request, effectively allowing them to manipulate the HTTP communication. The vulnerability is classified under CWE-1107, which describes "Improper Neutralization of Special Elements in HTTP Headers" and aligns with ATT&CK technique T1190, "Exploit Public-Facing Application," as it enables attackers to manipulate HTTP headers through crafted input. The flaw specifically affects the HTTP request construction module where the application fails to properly handle or sanitize user-supplied URLs that contain encoded control characters, creating an injection point that can be leveraged for various malicious purposes including cache poisoning, cookie manipulation, and authentication bypass.
The operational impact of CVE-2002-1405 extends beyond simple header injection, creating significant security implications for users who rely on Lynx for web browsing, particularly in environments where command-line usage is common. Attackers can exploit this vulnerability to inject false HTTP headers that may cause the browser to behave unexpectedly, potentially redirecting users to malicious websites or manipulating authentication tokens. The vulnerability is particularly concerning because it allows for HTTP response splitting attacks, where attackers can inject multiple HTTP responses into a single HTTP request, potentially leading to cache poisoning or cross-site scripting scenarios. This type of vulnerability is classified as a variant of the broader HTTP header injection attack pattern, which is commonly exploited in web application security breaches and is often categorized under the OWASP Top 10 as a critical security weakness. The impact is amplified in environments where Lynx is used for automated processes or when users frequently provide URLs through command-line interfaces, as these scenarios provide more opportunities for exploitation.
Mitigation strategies for CVE-2002-1405 require immediate implementation of input validation and sanitization measures within the Lynx browser's URL parsing functionality. System administrators should upgrade to Lynx version 2.8.5 or later, which includes proper input validation and sanitization for command-line parameters. The recommended approach involves implementing strict character filtering for URL inputs, particularly rejecting or encoding carriage return, line feed, and other control characters that could be used for header injection attacks. Organizations should also consider implementing network-level protections such as web application firewalls that can detect and block HTTP header injection attempts. Additionally, users should be educated about the risks of providing untrusted URLs through command-line arguments and encouraged to validate all input sources. The vulnerability demonstrates the critical importance of proper input sanitization in web applications and highlights the necessity of following secure coding practices as outlined in the OWASP Secure Coding Guidelines and ISO/IEC 27001 standards. Organizations should also implement monitoring solutions that can detect unusual HTTP header patterns that may indicate exploitation attempts, particularly in environments where Lynx is actively used for web access.