CVE-2018-4174 in macOS
Summary
by MITRE
An issue was discovered in certain Apple products. iOS before 11.3 is affected. macOS before 10.13.4 is affected. The issue involves the "Mail" component. It allows man-in-the-middle attackers to read S/MIME encrypted messages by leveraging an inconsistency in the user interface.
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Analysis
by VulDB Data Team • 07/27/2024
The vulnerability identified as CVE-2018-4174 represents a significant security flaw in Apple's Mail application affecting iOS versions prior to 11.3 and macOS versions prior to 10.13.4. This issue specifically targets the S/MIME encryption implementation within the mail client, creating a dangerous inconsistency between the application's security indicators and the actual encryption status of messages. The flaw enables man-in-the-middle attackers to potentially intercept and read sensitive S/MIME encrypted communications by exploiting a user interface inconsistency that misleads recipients about the true encryption state of incoming messages.
The technical nature of this vulnerability stems from how the Mail application presents encryption status indicators to users. When S/MIME encrypted messages are received, the application's user interface fails to properly communicate the actual encryption status, creating a scenario where users might believe a message is properly encrypted when it is not. This inconsistency allows attackers positioned between the sender and recipient to manipulate the communication flow, potentially intercepting messages that appear to be secure but are actually unencrypted or improperly encrypted. The vulnerability specifically affects the visual representation of encryption status within the mail client's interface, creating a deceptive user experience that undermines the security assumptions users make about their encrypted communications.
The operational impact of CVE-2018-4174 extends beyond simple message interception, as it fundamentally undermines user trust in the encryption verification process within Apple's Mail application. Organizations relying on S/MIME encryption for secure email communications would face potential data breaches where sensitive information could be accessed by unauthorized parties. The vulnerability affects any user who receives S/MIME encrypted messages through Apple's Mail application on affected platforms, making it particularly concerning for businesses, government agencies, and individuals who depend on email encryption for protecting confidential information. This flaw represents a critical failure in the security model of email encryption verification, where the user interface becomes a vector for attack rather than a security enhancement.
The security implications of this vulnerability align with CWE-693, which addresses protection mechanism failures in user interface components, and can be mapped to ATT&CK technique T1566 related to phishing and credential access through deceptive interfaces. Organizations should immediately implement mitigations including updating to affected Apple platforms, implementing additional email security measures beyond S/MIME, and educating users about the potential risks of relying solely on visual encryption indicators. The recommended remediation involves upgrading to iOS 11.3 or later and macOS 10.13.4 or later where Apple has addressed the inconsistency in the user interface presentation of encryption status. Security teams should also consider deploying additional email security solutions that provide independent verification of message encryption status, as the vulnerability demonstrates how user interface deception can create security vulnerabilities that bypass traditional technical controls.