CVE-2011-3253 in iOS
Summary
by MITRE
CalDAV in Apple iOS before 5 does not validate X.509 certificates for SSL sessions, which allows man-in-the-middle attackers to spoof calendar servers and obtain sensitive information via an arbitrary certificate.
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Analysis
by VulDB Data Team • 11/24/2021
The vulnerability described in CVE-2011-3253 represents a critical security flaw in Apple iOS versions prior to 5.0 that specifically affects the CalDAV implementation within the mobile operating system. This issue resides in the Secure Sockets Layer certificate validation mechanism, where the system fails to properly validate X.509 certificates during SSL sessions. The flaw creates a significant attack surface that enables malicious actors to conduct man-in-the-middle attacks against calendar services, compromising the integrity and confidentiality of calendar data. The vulnerability directly impacts the trust model that iOS relies upon for secure communication with calendar servers, fundamentally undermining the security assurances that users expect from their mobile devices.
The technical root cause of this vulnerability stems from the absence of proper certificate validation procedures within the iOS CalDAV client implementation. When iOS establishes SSL connections to calendar servers, it should verify the server's X.509 certificate against trusted certificate authorities and validate the certificate's authenticity, expiration dates, and proper domain matching. However, in affected iOS versions, this validation process is either completely bypassed or inadequately implemented, allowing attackers to present fraudulent certificates that appear legitimate to the client. This flaw aligns with CWE-295, which specifically addresses improper certificate validation in security protocols, and represents a classic example of insufficient certificate path validation that enables certificate spoofing attacks.
The operational impact of this vulnerability extends beyond simple calendar data compromise, as it provides attackers with a foothold for more sophisticated attacks. An attacker positioned in the network path between a user's iOS device and their calendar server can intercept communications and present a forged certificate that appears to be from a legitimate calendar service. This enables the attacker to not only read calendar entries, meeting details, and personal information but also to modify calendar data, potentially causing significant disruption to users' scheduling and business operations. The vulnerability affects the confidentiality, integrity, and availability of calendar services, representing a complete breakdown of the security model that iOS relies upon for secure communications. According to ATT&CK framework, this vulnerability maps to T1566.001 (Phishing via Service) and T1046 (Network Service Scanning) as attackers can exploit this weakness to establish persistent access to calendar data.
Organizations and individuals using affected iOS versions face significant risks from this vulnerability, as calendar data often contains sensitive personal and business information including meeting schedules, contact details, location data, and potentially confidential business communications. The impact is particularly severe in enterprise environments where calendar systems may contain proprietary information, strategic planning details, or sensitive operational data. Attackers can leverage this vulnerability to gain unauthorized access to calendar information that might reveal business strategies, personal schedules of executives, or other sensitive details that could be used for social engineering attacks. The vulnerability also enables attackers to manipulate calendar entries, potentially causing confusion, scheduling conflicts, or even security breaches through coordinated attacks on calendar-based authentication systems. Security professionals should note that this vulnerability demonstrates the critical importance of proper certificate validation in mobile security implementations and highlights the risks associated with inadequate cryptographic protocol enforcement in mobile operating systems.