CVE-2006-4390 in Mac OS X
Summary
by MITRE
CFNetwork in Apple Mac OS X 10.4 through 10.4.7 and 10.3.9 allows remote SSL sites to appear as trusted sites by using encryption without authentication, which can cause the lock icon in Safari to be displayed even when the site's identity cannot be trusted.
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Analysis
by VulDB Data Team • 04/23/2026
This vulnerability resides in the CFNetwork framework of Apple Mac OS X versions 10.3.9 and 10.4 through 10.4.7, representing a critical security flaw that undermines the fundamental trust mechanisms of secure web communications. The issue stems from how the system handles SSL/TLS certificate validation when sites employ encryption without proper authentication, creating a scenario where malicious actors can exploit this weakness to deceive users into believing they are connecting to legitimate secure sites. The vulnerability specifically affects the Safari web browser's visual trust indicators, particularly the lock icon that users rely upon to verify secure connections.
The technical flaw manifests when SSL sites implement encryption without proper certificate authentication, allowing the system to incorrectly validate connections as trusted even when the site's identity cannot be verified. This occurs because CFNetwork fails to properly enforce certificate validation requirements, creating a gap in the security chain that attackers can exploit to present fake SSL certificates as legitimate. The vulnerability is classified under CWE-295 which addresses "Improper Certificate Validation" and aligns with ATT&CK technique T1059.001 for command and scripting interpreter. When a user visits an affected site, the browser displays the secure lock icon despite the connection potentially being compromised, creating a false sense of security that can lead to credential theft or data interception.
The operational impact of this vulnerability extends beyond simple user deception, as it enables sophisticated man-in-the-middle attacks where attackers can intercept sensitive communications without detection. Users accessing websites through Safari on affected Mac OS X systems may unknowingly transmit personal information, login credentials, or financial data to malicious servers that appear to be legitimate secure sites. This vulnerability particularly affects corporate environments where employees may access sensitive company resources through potentially compromised connections, and it represents a significant risk to e-commerce transactions and secure communications. The flaw undermines the core security model of SSL/TLS protocols and demonstrates a critical failure in the certificate validation process that should have been enforced by the operating system.
Mitigation strategies for this vulnerability include immediate system updates to patched versions of Mac OS X, which address the certificate validation logic in CFNetwork. Organizations should implement network monitoring to detect unusual SSL certificate behavior and consider deploying additional security layers such as extended validation certificates or certificate pinning mechanisms. Security administrators should also educate users about the importance of verifying certificate details beyond the lock icon, particularly when accessing sensitive sites. The vulnerability highlights the importance of proper certificate validation as outlined in RFC 5280 and emphasizes the need for comprehensive security testing of cryptographic implementations. Organizations should also consider implementing network segmentation and additional authentication mechanisms to reduce the impact of such vulnerabilities in their environments.