CVE-2017-13874 in iOS
Summary
by MITRE
An issue was discovered in certain Apple products. iOS before 11.2 is affected. The issue involves the "Mail" component. It might allow remote attackers to bypass an intended encryption protection mechanism by leveraging incorrect S/MIME certificate selection.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 01/26/2021
The vulnerability identified as CVE-2017-13874 represents a significant security flaw within Apple's iOS Mail application affecting versions prior to 11.2. This issue specifically targets the S/MIME encryption mechanism that users rely upon to secure their email communications. The flaw exists within the certificate selection process during email encryption operations, creating a potential pathway for malicious actors to undermine the intended security protections that S/MIME is designed to provide. The vulnerability demonstrates how cryptographic mechanisms can be subverted through improper implementation of certificate validation processes, potentially exposing sensitive email communications to unauthorized access.
The technical nature of this vulnerability stems from incorrect certificate selection logic within the Mail application's S/MIME implementation. When users attempt to encrypt emails using S/MIME, the system should properly validate and select appropriate certificates based on established security criteria and certificate authority trust relationships. However, the flawed implementation allows attackers to manipulate the certificate selection process, potentially enabling them to select weaker or compromised certificates that bypass the intended encryption strength. This weakness specifically relates to how the system handles certificate validation during the encryption process, where the proper certificate chain verification mechanisms are not adequately enforced, creating an opportunity for man-in-the-middle attacks or certificate substitution scenarios.
From an operational perspective, this vulnerability poses substantial risks to users who rely on S/MIME encryption for protecting sensitive communications. The impact extends beyond simple data confidentiality concerns as it undermines the trust model that S/MIME establishes between communicating parties. Attackers could exploit this weakness to decrypt intercepted emails, impersonate legitimate senders, or gain unauthorized access to information that should remain protected through cryptographic means. The remote nature of the attack vector means that users are vulnerable even when accessing their email from secure networks, as the vulnerability exists within the client-side application processing rather than network transmission protocols. This type of vulnerability particularly affects enterprise environments where email encryption is a critical component of information security policies and compliance requirements.
Organizations and individual users should immediately update to iOS 11.2 or later versions to remediate this vulnerability, as Apple released the update specifically to address the certificate selection flaw. The mitigation strategy should also include reviewing existing S/MIME configurations and implementing additional monitoring for suspicious certificate usage patterns. Security teams should consider conducting vulnerability assessments to identify systems that may still be running vulnerable iOS versions and ensure proper certificate management practices are in place. This vulnerability aligns with CWE-310, which addresses cryptographic weaknesses, and represents a specific implementation flaw that could be categorized under ATT&CK technique T1566 for social engineering attacks that leverage cryptographic bypass mechanisms. The flaw demonstrates the importance of proper certificate validation and the potential consequences when cryptographic implementation details are not carefully considered during security-sensitive application development processes.