CVE-2002-0862 in Windows
Summary
by MITRE
The (1) CertGetCertificateChain, (2) CertVerifyCertificateChainPolicy, and (3) WinVerifyTrust APIs within the CryptoAPI for Microsoft products including Microsoft Windows 98 through XP, Office for Mac, Internet Explorer for Mac, and Outlook Express for Mac, do not properly verify the Basic Constraints of intermediate CA-signed X.509 certificates, which allows remote attackers to spoof the certificates of trusted sites via a man-in-the-middle attack for SSL sessions, as originally reported for Internet Explorer and IIS.
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Analysis
by VulDB Data Team • 06/22/2025
The vulnerability described in CVE-2002-0862 represents a critical flaw in the Windows CryptoAPI implementation that affects multiple Microsoft products including Windows 98 through XP, Office for Mac, Internet Explorer for Mac, and Outlook Express for Mac. This security weakness stems from improper validation of X.509 certificate Basic Constraints extension, which is a fundamental component of certificate chain validation. The Basic Constraints extension is designed to indicate whether a certificate is a CA certificate and to specify the maximum depth of valid certification paths. When this extension is not properly verified, it creates a pathway for malicious actors to exploit the certificate validation process.
The technical flaw manifests in three specific CryptoAPI functions: CertGetCertificateChain, CertVerifyCertificateChainPolicy, and WinVerifyTrust. These functions are responsible for validating certificate chains and ensuring the trustworthiness of digital certificates used in secure communications. The vulnerability occurs because these APIs fail to properly enforce the Basic Constraints extension requirements when processing intermediate CA-signed certificates. This allows attackers to construct fraudulent certificate chains where intermediate certificates do not properly declare their CA status or exceed the allowed path length, creating a scenario where malicious certificates can appear valid to the system.
The operational impact of this vulnerability is severe and directly enables man-in-the-middle attacks against SSL sessions. When attackers can successfully spoof certificates from trusted sites, they gain the ability to intercept and potentially modify encrypted communications between users and web servers. This compromises the integrity and confidentiality of data transmitted over SSL/TLS connections, affecting web browsing security, email communications, and any other applications relying on certificate-based authentication. The vulnerability is particularly dangerous because it affects the core cryptographic validation mechanisms that protect internet communications, making it a significant threat to the overall security posture of affected systems.
The attack vector for this vulnerability involves an attacker positioned between a client and a legitimate server, capable of intercepting and modifying network traffic. By constructing malicious certificate chains that bypass the Basic Constraints validation, attackers can present forged certificates that appear legitimate to vulnerable systems. This enables them to perform SSL stripping attacks, decrypt sensitive communications, and potentially inject malicious content into web sessions. The vulnerability affects the fundamental trust model of internet security, where the integrity of certificate validation is paramount for maintaining secure communications.
Organizations affected by this vulnerability should implement immediate mitigations including applying Microsoft security patches, updating certificate trust stores, and implementing additional network security measures such as certificate pinning. The vulnerability aligns with CWE-330 use of insecure random number, though it is more specifically related to certificate validation weaknesses. From an ATT&CK perspective, this vulnerability maps to T1552.001 for unsecured credentials and T1041 for data compression, as it enables attackers to establish persistent access through compromised SSL communications. System administrators should also consider implementing network monitoring to detect potential certificate manipulation attempts and establish more robust certificate validation policies beyond the default CryptoAPI behavior.