CVE-2008-4491 in Mail
Summary
by MITRE
Apple Mail.app 3.5 on Mac OS X, when "Store draft messages on the server" is enabled, stores draft copies of S/MIME email in plaintext on the email server, which allows server owners and remote man-in-the-middle attackers to read sensitive mail.
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Analysis
by VulDB Data Team • 10/11/2018
This vulnerability exists in Apple Mail.app version 3.5 running on Mac OS X systems where the "Store draft messages on the server" feature is enabled. The flaw represents a critical security oversight in how email clients handle sensitive cryptographic content during the draft storage process. When users compose S/MIME encrypted emails and save them as drafts on the server, the application fails to maintain the encryption integrity of these messages, instead storing them in plaintext format on the remote mail server infrastructure. This behavior creates a significant attack surface that exposes sensitive email content to unauthorized access through multiple threat vectors.
The technical implementation flaw stems from the application's failure to properly encrypt draft messages when they are stored on the server, despite the fact that the final email transmission may be properly encrypted using S/MIME protocols. This represents a violation of fundamental security principles where the confidentiality of data in transit and at rest should be maintained consistently throughout the email lifecycle. The vulnerability specifically affects the server-side storage mechanism and demonstrates poor cryptographic implementation practices that leave sensitive information exposed during intermediate states of email processing. The issue is classified under CWE-312 as "Cleartext Storage of Sensitive Information" and represents a failure in data protection during storage phases of the information security lifecycle.
The operational impact of this vulnerability is severe as it allows both legitimate server administrators and malicious remote attackers to access sensitive email content that should remain confidential. Server owners with administrative privileges can directly read stored draft messages, while man-in-the-middle attackers can intercept and access these plaintext drafts during network transmission between the client and server. This creates a persistent threat vector where sensitive corporate communications, personal information, and potentially classified data could be exposed to unauthorized parties. The vulnerability is particularly concerning in enterprise environments where email drafts often contain confidential business information, strategic planning details, or personal identifiable information that could be exploited for financial gain or corporate espionage.
Organizations should immediately disable the "Store draft messages on the server" feature in Apple Mail.app when handling sensitive communications to prevent this vulnerability from being exploited. System administrators should implement network monitoring to detect potential man-in-the-middle attacks and consider deploying additional encryption layers for email storage. The recommended mitigation includes configuring email clients to store drafts locally rather than on remote servers, implementing proper network security controls such as encrypted connections, and conducting regular security assessments to identify similar cryptographic implementation flaws. This vulnerability demonstrates the importance of maintaining end-to-end encryption throughout all phases of data processing and storage, aligning with ATT&CK technique T1566 for credential access through man-in-the-middle attacks and T1552 for data protection bypass through cleartext storage of sensitive information.