CVE-1999-1113 is a medium severity vulnerability affecting Eudora Internet Mail Server (EIMS) versions 1.2 and 2.0 and earlier running on MacOS systems. The vulnerability is a buffer overflow triggered by sending an excessively long USER command to the server's listening port 106. This buffer overflow can be exploited remotely by an unauthenticated attacker without user interaction, resulting in a denial of service (DoS) condition. Specifically, the overflow causes the mail server process to crash or become unresponsive, disrupting email services. The vulnerability does not impact confidentiality or integrity directly, as it does not allow code execution or data leakage, but it affects availability by causing service outages. The vulnerability was published in 1998, and no patches are available, indicating that the affected software is likely obsolete. The CVSS v2 score is 5.0, reflecting network attack vector, low complexity, no authentication required, no confidentiality or integrity impact, but partial availability impact. There are no known exploits in the wild currently. The vulnerability is specific to MacOS versions of EIMS and does not affect other platforms or mail servers.

For European organizations, the impact of this vulnerability is limited due to the age and obsolescence of the affected software. Modern mail servers have long replaced Eudora Internet Mail Server, and MacOS server usage for mail services is minimal in enterprise environments. However, any legacy systems still running EIMS on MacOS could be vulnerable to remote denial of service attacks, potentially disrupting internal or external email communications. This could impact business continuity, especially for organizations relying on legacy infrastructure without proper segmentation or monitoring. The lack of patch availability means organizations cannot remediate the vulnerability through updates, increasing the risk if such legacy systems remain in use. Given the vulnerability only causes DoS and not data breach or code execution, the impact on confidentiality and integrity is negligible. Overall, the threat is low for most European organizations but could be moderate for those with legacy MacOS mail servers still exposed to the internet.

Since no patch is available for this vulnerability, organizations should take compensating controls to mitigate risk. First, identify and inventory any legacy Eudora Internet Mail Server installations on MacOS within the network. These systems should be isolated from external networks and segmented internally to limit exposure. Disable or block inbound traffic to port 106 at firewalls and network perimeter devices to prevent remote exploitation attempts. If the mail server is no longer required, decommission and remove it to eliminate the attack surface. Implement network intrusion detection or prevention systems (IDS/IPS) with signatures to detect anomalous long USER commands targeting port 106. Regularly monitor logs for unusual connection attempts or crashes related to the mail server. Finally, plan migration to modern, supported mail server solutions that receive security updates and patches.