CVE-2011-0228 in iOS
Summary
by MITRE
The Data Security component in Apple iOS before 4.2.10 and 4.3.x before 4.3.5 does not check the basicConstraints parameter during validation of X.509 certificate chains, which allows man-in-the-middle attackers to spoof an SSL server by using a non-CA certificate to sign a certificate for an arbitrary domain.
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Analysis
by VulDB Data Team • 04/03/2017
The vulnerability identified as CVE-2011-0228 represents a critical flaw in Apple iOS cryptographic validation mechanisms that persisted across multiple versions of the operating system. This weakness specifically affects the Data Security component responsible for X.509 certificate chain validation processes, creating a significant security gap that adversaries could exploit to conduct man-in-the-middle attacks. The issue manifests when the iOS system fails to properly validate the basicConstraints parameter within certificate chains, a fundamental requirement for establishing proper certificate authority relationships. This failure allows attackers to craft certificates that appear legitimate while bypassing essential security checks that should prevent non-certification authority certificates from signing domains they do not control.
The technical flaw stems from the iOS system's inadequate certificate validation logic that omits crucial basicConstraints checking during X.509 certificate chain processing. The basicConstraints parameter in X.509 certificates serves as a critical indicator that defines whether a certificate can function as a certificate authority and specifies the maximum depth of certificate chains that can be validated. When this parameter is ignored, the system accepts certificates that should never be trusted for server authentication purposes. This vulnerability directly maps to CWE-331, which addresses insufficient entropy in cryptographic operations, though more specifically relates to certificate validation failures. Attackers can exploit this by obtaining a valid certificate from a legitimate CA and then using it to sign a certificate for a target domain without proper authorization, effectively creating a fraudulent certificate that iOS accepts as legitimate due to the missing validation step.
The operational impact of this vulnerability extends far beyond simple network security concerns, as it fundamentally undermines the trust model that secure communications rely upon. Mobile devices running affected iOS versions become vulnerable to sophisticated attacks where adversaries can intercept and modify encrypted communications between users and web services. This capability allows attackers to eavesdrop on sensitive data transmissions, manipulate transactional communications, and potentially gain access to user credentials, financial information, and private communications. The vulnerability affects all network services that depend on SSL/TLS encryption, including email services, web browsers, banking applications, and corporate communication platforms, making it particularly dangerous in enterprise environments where mobile device security is paramount. According to ATT&CK framework domain T1573.002, this vulnerability enables adversaries to perform secure network communication evasion techniques by establishing fraudulent trust relationships that bypass normal security controls.
The exploitation of CVE-2011-0228 requires attackers to possess the ability to create or obtain a certificate from a legitimate CA, then use that certificate to sign fraudulent certificates for target domains. This process typically involves the attacker obtaining a valid certificate that can be used as a foundation for creating a fraudulent certificate chain that appears legitimate to iOS systems. The vulnerability affects iOS versions including all builds before 4.2.10 and 4.3.5, meaning that users who had not updated their devices were at risk of exploitation. Organizations and individuals could be targeted through various attack vectors including phishing campaigns, compromised websites, or network interception attacks where attackers positioned themselves between users and legitimate services. The attack surface is particularly broad due to the widespread adoption of iOS devices and the reliance on SSL/TLS for secure communications across numerous applications and services. Remediation efforts required immediate deployment of iOS updates, with Apple releasing patches that corrected the certificate validation logic to properly enforce basicConstraints checking. Security professionals should have implemented network monitoring solutions to detect potential exploitation attempts and conducted comprehensive vulnerability assessments to identify devices running affected iOS versions. The vulnerability also highlighted the importance of maintaining up-to-date cryptographic validation mechanisms and underscored the critical need for proper certificate authority validation processes in mobile security implementations.