CVE-1999-1113 in Eudora Internet Mail Server
Summary
by MITRE
Buffer overflow in Eudora Internet Mail Server (EIMS) 2.01 and earlier on MacOS systems allows remote attackers to cause a denial of service via a long USER command to port 106.
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Analysis
by VulDB Data Team • 11/25/2024
The vulnerability identified as CVE-1999-1113 represents a critical buffer overflow flaw within the Eudora Internet Mail Server version 2.01 and earlier implementations running on MacOS platforms. This issue specifically manifests when the server processes incoming USER commands on port 106, which is the standard port for the POP3 protocol used by email clients to retrieve messages from mail servers. The buffer overflow occurs due to inadequate input validation and bounds checking within the server's command processing routine, creating a scenario where maliciously crafted input can overwrite adjacent memory locations beyond the allocated buffer space.
The technical exploitation of this vulnerability leverages the fundamental weakness in how the EIMS server handles user authentication commands. When a remote attacker sends a specially crafted USER command containing an excessive amount of data, the server's parsing function fails to properly validate the input length against the allocated buffer capacity. This memory corruption results in the overwrite of critical program variables, stack pointers, or return addresses, ultimately causing the server process to crash and terminate unexpectedly. The vulnerability operates at the application layer of the network stack, making it particularly dangerous as it requires no authentication or privileged access to exploit, allowing attackers to remotely disrupt service availability.
The operational impact of this buffer overflow vulnerability extends beyond simple service disruption to potentially enable more sophisticated attack vectors. While the primary effect manifests as a denial of service condition that prevents legitimate users from accessing their email accounts, the underlying memory corruption could theoretically be exploited to execute arbitrary code if proper memory protection mechanisms were not in place. The vulnerability affects the core functionality of the email server, rendering it unavailable to authorized users and potentially providing attackers with a foothold for further reconnaissance activities. This type of vulnerability directly impacts the availability aspect of the CIA triad and represents a classic example of a remote code execution vulnerability that can be leveraged for service disruption.
Mitigation strategies for this vulnerability require immediate implementation of software updates and patches provided by the vendor, as well as network-level protections to restrict access to port 106 until the fix is deployed. System administrators should implement proper input validation controls and consider deploying intrusion detection systems that can identify suspicious USER command patterns. The vulnerability aligns with CWE-121, which categorizes buffer overflow conditions as a fundamental weakness in data handling, and represents a specific instance of the broader ATT&CK technique T1499.200 related to network denial of service attacks. Organizations should also consider implementing network segmentation to isolate critical email services and establish proper monitoring procedures to detect abnormal command patterns that may indicate exploitation attempts. The remediation process involves not only patching the vulnerable software but also reviewing and strengthening the overall security posture of email infrastructure to prevent similar vulnerabilities from emerging in other components of the system.