CVE-2001-0338 in Internet Explorer
Summary
by MITRE
Internet Explorer 5.5 and earlier does not properly validate digital certificates when Certificate Revocation List (CRL) checking is enabled, which could allow remote attackers to spoof trusted web sites, aka the "Server certificate validation vulnerability."
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Analysis
by VulDB Data Team • 04/07/2017
The vulnerability identified as CVE-2001-0338 represents a critical weakness in Microsoft Internet Explorer versions 5.5 and earlier that fundamentally undermines the security of SSL/TLS certificate validation processes. This flaw occurs when Certificate Revocation List checking is enabled, creating a scenario where the browser fails to properly validate digital certificates presented by web servers. The vulnerability stems from insufficient certificate validation logic that allows attackers to exploit a weakness in the certificate chain verification process, potentially enabling man-in-the-middle attacks against unsuspecting users. According to CWE-295, this represents a failure in certificate validation mechanisms that directly impacts the trust model of secure web communications. The vulnerability operates at the application layer of the OSI model, specifically affecting the transport layer security implementation within the web browser's security framework.
The technical flaw manifests when Internet Explorer attempts to validate server certificates against certificate revocation lists, but fails to properly check the certificate chain or validate that certificates have not been revoked. This allows attackers to present forged certificates that appear legitimate to the browser, effectively bypassing the security controls designed to prevent impersonation attacks. The vulnerability specifically affects the certificate validation routine that should verify certificate status against CRLs, which are lists of certificates that have been revoked by certificate authorities. Attackers can exploit this by creating malicious certificates that pass the browser's validation checks, enabling them to impersonate trusted websites without detection. This weakness directly violates the principles of authentication and integrity that are fundamental to secure communications, as outlined in the NIST SP 800-57 security standards for cryptographic key management.
The operational impact of this vulnerability extends far beyond simple certificate validation failures, as it enables sophisticated phishing and impersonation attacks that can compromise user credentials and sensitive data. When attackers successfully exploit this vulnerability, they can establish secure connections with users while appearing to be legitimate websites, making it extremely difficult for end users to detect malicious activity. The attack surface includes any web service that relies on SSL/TLS certificates for authentication and encryption, potentially affecting banking, e-commerce, and corporate web applications. This vulnerability particularly impacts organizations that depend on Internet Explorer for business-critical applications, as it undermines the trust model that enables secure web transactions. The attack vector requires minimal sophistication, making it particularly dangerous as it can be exploited by threat actors with limited technical expertise, as classified under ATT&CK technique T1566 for credential harvesting through phishing.
Mitigation strategies for CVE-2001-0338 require immediate patching of affected Internet Explorer versions, as Microsoft released security updates specifically addressing this certificate validation flaw. Organizations should implement certificate pinning mechanisms where possible, though this approach requires careful planning and management to avoid service disruptions. Network administrators should monitor for suspicious certificate usage and implement additional security controls such as web application firewalls that can detect and block certificate-based attacks. The vulnerability highlights the importance of maintaining up-to-date security patches and demonstrates the critical nature of certificate validation in secure communications. Organizations should also consider implementing additional layers of authentication and monitoring to detect potential exploitation attempts, as the vulnerability affects the fundamental security model of web browsers. This issue underscores the necessity of comprehensive security testing and validation of cryptographic implementations, particularly in widely deployed applications where certificate validation failures can have widespread consequences across multiple security domains.