CVE-2007-2291 in Internet Explorer
Summary
by MITRE
CRLF injection vulnerability in the Digest Authentication support for Microsoft Internet Explorer 7.0.5730.11 allows remote attackers to conduct HTTP response splitting attacks via a LF (%0a) in the username attribute.
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Analysis
by VulDB Data Team • 07/14/2021
The vulnerability identified as CVE-2007-2291 represents a critical CRLF injection flaw within Microsoft Internet Explorer 7.0.5730.11's Digest Authentication implementation. This security weakness specifically affects the handling of username attributes during HTTP digest authentication processes, creating an avenue for sophisticated attack vectors that can compromise web application security. The vulnerability stems from inadequate input validation and sanitization of authentication credentials, particularly when processing the username parameter in digest authentication challenges.
The technical exploitation of this vulnerability occurs through the manipulation of the username attribute to include line feed characters represented as %0a in the HTTP request. When Internet Explorer processes these malformed credentials during digest authentication, the CRLF characters are not properly escaped or filtered, allowing attackers to inject additional HTTP headers into the response. This injection capability enables attackers to manipulate the HTTP response stream, effectively splitting the response and potentially injecting malicious content or redirecting users to malicious websites. The vulnerability specifically targets the digest authentication mechanism where the username parameter is processed without adequate sanitization of control characters that could alter the HTTP protocol flow.
The operational impact of this vulnerability extends beyond simple authentication bypasses, as it enables HTTP response splitting attacks that can lead to various downstream security consequences. Attackers can leverage this flaw to perform session hijacking, cache poisoning, cross-site scripting attacks, or redirect users to malicious sites by injecting additional headers into the HTTP response. The vulnerability affects web applications that rely on Internet Explorer 7.0 for digest authentication, creating a significant risk for organizations where this browser version is still in use. This weakness aligns with CWE-113, which describes improper neutralization of CRLF characters in HTTP headers, and represents a classic example of HTTP response splitting vulnerabilities that have been documented in security literature for years.
Mitigation strategies for this vulnerability require immediate attention from system administrators and security teams. The primary remediation involves upgrading to a patched version of Internet Explorer 7.0 or implementing server-side protections that sanitize authentication parameters before they are processed. Organizations should implement input validation mechanisms that filter out control characters from username attributes during digest authentication processes. Network security controls such as web application firewalls can be configured to detect and block requests containing CRLF sequences in authentication parameters. Additionally, security teams should consider implementing proper HTTP header sanitization practices and ensure that all authentication mechanisms properly escape special characters to prevent protocol-level injection attacks. The vulnerability demonstrates the importance of adhering to security best practices for HTTP header handling and input validation, as outlined in various security frameworks including the OWASP Top Ten and NIST guidelines for secure coding practices.