CVE-2000-0075 in MsgCore
Summary
by MITRE
Super Mail Transfer Package (SMTP), later called MsgCore, has a memory leak which allows remote attackers to cause a denial of service by repeating multiple HELO, MAIL FROM, RCPT TO, and DATA commands in the same session.
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Analysis
by VulDB Data Team • 10/19/2025
The vulnerability identified as CVE-2000-0075 affects the Super Mail Transfer Package SMTP implementation, which was later renamed MsgCore, presenting a significant security weakness that enables remote attackers to execute denial of service attacks. This memory leak vulnerability manifests through the repeated execution of fundamental SMTP protocol commands within a single session, specifically targeting the HELO, MAIL FROM, RCPT TO, and DATA command sequences. The flaw represents a classic example of insufficient resource management where the application fails to properly release allocated memory resources during the normal SMTP transaction process, leading to progressive memory consumption that eventually exhausts available system resources.
The technical implementation of this vulnerability stems from the application's failure to maintain proper state management and memory cleanup procedures during extended SMTP sessions. When an attacker repeatedly submits these commands in sequence without properly terminating the session, the system accumulates memory allocations that are never freed, creating a gradual but steady increase in memory usage. This behavior aligns with CWE-401, which categorizes memory leaks as a common weakness in software design where allocated memory is not properly deallocated. The vulnerability operates at the protocol level, exploiting the SMTP transaction model where each command sequence should ideally be processed and cleaned up before proceeding to the next, but instead allows for continuous accumulation of memory resources.
The operational impact of this vulnerability extends beyond simple resource exhaustion, as it can effectively disable the mail server's ability to process legitimate email transactions. Attackers can maintain persistent sessions while continuously consuming memory resources, leading to system instability and complete service unavailability. The attack vector requires minimal complexity as it only necessitates establishing an SMTP connection and repeatedly sending the specified commands, making it particularly dangerous for systems that handle high volumes of email traffic. This vulnerability directly impacts the availability aspect of the CIA triad and can be classified under the MITRE ATT&CK framework's T1499.004 technique for network denial of service, where adversaries leverage protocol weaknesses to exhaust system resources.
Mitigation strategies for this vulnerability involve implementing proper memory management practices and session timeout mechanisms within the SMTP implementation. System administrators should configure automatic session timeouts to prevent prolonged connections from consuming excessive resources, while the application itself must ensure that all allocated memory is properly deallocated after each command sequence. Additionally, implementing rate limiting and connection throttling mechanisms can help prevent the exploitation of this vulnerability by limiting the frequency of command repetitions within a single session. The fix requires developers to properly implement the SMTP protocol state machine with appropriate cleanup routines and to address the underlying memory allocation patterns that lead to resource accumulation. Organizations should also consider deploying intrusion detection systems that can identify unusual command repetition patterns that may indicate exploitation attempts, providing an additional layer of protection against this specific class of denial of service attacks.