CVE-2011-0199 in Mac OS X
Summary
by MITRE
The Certificate Trust Policy component in Apple Mac OS X before 10.6.8 does not perform CRL checking for Extended Validation (EV) certificates that lack OCSP URLs, which might allow man-in-the-middle attackers to spoof an SSL server via a revoked certificate.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 01/21/2025
The vulnerability described in CVE-2011-0199 represents a critical flaw in Apple Mac OS X operating systems prior to version 10.6.8, specifically within the Certificate Trust Policy component. This weakness stems from the operating system's failure to implement proper Certificate Revocation List (CRL) checking for Extended Validation certificates that do not contain Online Certificate Status Protocol (OCSP) URLs. The absence of this crucial validation mechanism creates a significant security gap that adversaries can exploit to conduct man-in-the-middle attacks against SSL/TLS connections. Extended Validation certificates are designed to provide higher assurance of identity through rigorous verification processes, making their proper validation even more critical for maintaining secure communications.
The technical flaw manifests when the system encounters EV certificates lacking OCSP URLs, which are typically used to provide real-time certificate status information. In the absence of OCSP support, the system should fall back to CRL checking to verify certificate validity, but this fallback mechanism was not properly implemented in affected Mac OS X versions. This creates a scenario where attackers can obtain revoked certificates and successfully establish fraudulent SSL connections, as the operating system cannot reliably determine that the certificate has been compromised or revoked. The vulnerability specifically affects the trust validation process that occurs during SSL/TLS handshakes, where the client verifies the server's certificate chain and ensures all certificates in the chain are valid and not revoked.
The operational impact of this vulnerability extends beyond simple certificate validation failures, as it fundamentally undermines the security assurances provided by SSL/TLS protocols. Attackers can leverage this weakness to impersonate legitimate servers, intercept sensitive communications, and potentially access confidential data transmitted over supposedly secure connections. This vulnerability particularly affects web browsing, email communications, and any application relying on SSL/TLS for secure data transmission. The risk is amplified because EV certificates are often used by financial institutions, government agencies, and other organizations that handle highly sensitive information, making successful exploitation potentially devastating. The vulnerability also affects the broader trust model of the operating system, as it demonstrates a failure in the certificate validation infrastructure that could potentially extend to other certificate types or protocols.
Organizations and users affected by this vulnerability should immediately apply the security patches provided by Apple through the Mac OS X 10.6.8 update or later versions. System administrators should conduct comprehensive vulnerability assessments to identify any systems running affected versions of Mac OS X and ensure proper patch management protocols are in place. Network monitoring should be enhanced to detect potential man-in-the-middle attacks, particularly in environments where SSL/TLS communications are heavily used. The vulnerability aligns with CWE-295, which addresses improper certificate validation, and represents a specific implementation weakness in the certificate trust validation process. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access and defense evasion, as attackers can leverage it to establish persistent access to secure communications channels while potentially avoiding detection mechanisms that rely on proper certificate validation. The incident underscores the critical importance of maintaining up-to-date security patches and implementing robust certificate management practices to prevent exploitation of trust validation weaknesses in operating system components.