CVE-2018-4111 in macOS
Summary
by MITRE
An issue was discovered in certain Apple products. 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 message content by sending HTML e-mail that references remote resources but lacks a valid S/MIME signature.
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Analysis
by VulDB Data Team • 07/27/2024
The vulnerability identified as CVE-2018-4111 represents a significant security flaw in Apple's Mail application affecting macOS versions prior to 10.13.4. This issue specifically targets the S/MIME encryption mechanism that users rely on to secure their email communications. The vulnerability stems from how the Mail application handles HTML email content that references external resources while lacking proper S/MIME signatures, creating a dangerous gap in email security protocols. The flaw essentially undermines the cryptographic protection that S/MIME is designed to provide, allowing malicious actors to intercept and read sensitive information that should remain encrypted.
The technical nature of this vulnerability can be categorized under CWE-310 as it involves cryptographic weaknesses in the handling of encrypted email content. The vulnerability operates through a man-in-the-middle attack vector where an attacker can manipulate HTML email content to reference remote resources that are not properly authenticated. When the Mail application processes such emails, it fails to adequately verify that the referenced resources are legitimate and properly signed, thereby allowing the attacker to access the plaintext content that should have been protected by S/MIME encryption. This represents a fundamental breakdown in the application's security model for handling mixed content in email messages.
The operational impact of CVE-2018-4111 extends beyond simple information disclosure, as it fundamentally compromises the trust model that S/MIME encryption is designed to establish. Organizations relying on S/MIME-encrypted emails for sensitive communications face potential data breaches where confidential information can be intercepted and read by unauthorized parties. The vulnerability affects users who may not be security-savvy and could unknowingly receive malicious emails that exploit this weakness. Attackers can leverage this vulnerability to target corporate executives, financial institutions, or any organization that depends on secure email communications, potentially leading to financial losses, intellectual property theft, or reputational damage. The attack requires minimal technical expertise and can be executed through standard email traffic, making it particularly dangerous in enterprise environments.
Mitigation strategies for this vulnerability primarily involve upgrading to macOS 10.13.4 or later versions where Apple has implemented proper validation of S/MIME signatures and HTML content references. System administrators should ensure all affected devices receive timely security updates and consider implementing additional email security measures such as content filtering, email encryption policies, and user education programs. The vulnerability highlights the importance of maintaining current operating system versions and the critical need for organizations to have robust patch management processes in place. Additionally, users should be trained to recognize suspicious email patterns and understand the limitations of email encryption when dealing with mixed content types. This vulnerability serves as a reminder of the complex security challenges that arise when implementing encryption protocols in email applications and the necessity of comprehensive security testing for all components that handle sensitive data.