CVE-1999-0429 in Lotus Notes
Summary
by MITRE
The Lotus Notes 4.5 client may send a copy of encrypted mail in the clear across the network if the user does not set the "Encrypt Saved Mail" preference.
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Analysis
by VulDB Data Team • 04/18/2026
The vulnerability described in CVE-1999-0429 represents a critical security flaw in the Lotus Notes 4.5 client software that directly impacts the confidentiality of email communications. This issue stems from a misconfiguration in the client's encryption handling mechanism, where the system fails to properly enforce encryption policies even when users have explicitly enabled encryption for outgoing messages. The vulnerability specifically affects the transport layer security of email communications, creating a scenario where encrypted content can be transmitted in plaintext form across network connections when certain user preferences are not properly configured.
The technical flaw manifests in the client's failure to validate or enforce the encryption state of messages before transmission, particularly when the "Encrypt Saved Mail" preference is disabled. This configuration oversight creates a security boundary violation where the system assumes that encrypted messages should remain encrypted throughout their lifecycle, including during network transmission. The vulnerability operates at the application layer of the network stack, where the Lotus Notes client processes email messages and determines their security attributes before network delivery. When users disable the specific preference for encrypting saved mail, the client incorrectly assumes that the message should be transmitted in its unencrypted form regardless of the encryption status of the message itself. This represents a fundamental flaw in the client's security policy enforcement mechanism.
The operational impact of this vulnerability is significant for organizations relying on Lotus Notes for secure communications. Attackers who can intercept network traffic between Lotus Notes clients can potentially access sensitive information that was intended to be encrypted, undermining the confidentiality assurances that users expect from their email systems. The vulnerability affects both internal communications and external email exchanges, creating potential exposure for intellectual property, personal data, and business communications. Organizations may experience compliance violations with data protection regulations such as the Sarbanes-Oxley Act or HIPAA, depending on the nature of the information being transmitted. The impact extends beyond individual user privacy concerns to encompass organizational security posture and regulatory compliance requirements.
Mitigation strategies for this vulnerability should focus on enforcing proper configuration management and user education. System administrators must ensure that the "Encrypt Saved Mail" preference is enabled by default and that users understand the security implications of disabling encryption features. The implementation of group policies or configuration management tools can help enforce consistent security settings across all client installations. Additionally, network monitoring solutions should be deployed to detect unusual traffic patterns that might indicate unauthorized plaintext transmission of encrypted content. Organizations should also consider implementing network segmentation and encryption at multiple layers to provide defense in depth. This vulnerability aligns with CWE-310, which addresses cryptographic weakness, and represents a violation of the principle of least privilege as outlined in the ATT&CK framework under the execution and persistence domains. Regular security audits and penetration testing should be conducted to verify that encryption policies are properly enforced and that no unauthorized bypass mechanisms exist within the Lotus Notes environment.