CVE-2000-0971 in Mail Server
Summary
by MITRE
Avirt Mail 4.0 and 4.2 allows remote attackers to cause a denial of service and possibly execute arbitrary commands via a long "RCPT TO" or "MAIL FROM" command.
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Analysis
by VulDB Data Team • 02/02/2025
The vulnerability identified as CVE-2000-0971 affects Avirt Mail versions 4.0 and 4.2, representing a critical security flaw that enables remote attackers to disrupt service availability and potentially execute unauthorized commands on affected systems. This issue stems from inadequate input validation within the mail server's command processing mechanism, specifically when handling email address specifications in the RCPT TO and MAIL FROM SMTP commands. The vulnerability operates at the application layer of the network stack, exploiting the lack of proper boundary checks on command parameters that are typically used to define email recipient and sender addresses during the email transmission process.
The technical implementation of this flaw involves buffer overflow conditions that occur when the mail server receives excessively long argument strings in either the RCPT TO or MAIL FROM SMTP commands. When these commands exceed the allocated buffer space, the system experiences memory corruption that can result in application crashes, system instability, and in some cases, arbitrary code execution. The vulnerability manifests as a denial of service condition when the server becomes unresponsive due to the overflow, but the potential for remote code execution emerges when the buffer overflow allows attackers to manipulate the program execution flow. This type of vulnerability falls under the CWE-121 category of buffer overflow conditions, specifically representing a classic stack-based buffer overflow that can be exploited through improper input handling.
The operational impact of this vulnerability extends beyond simple service disruption to potentially enable full system compromise when exploited successfully. Remote attackers can leverage this weakness to gain unauthorized access to mail server systems, potentially leading to data breaches, email spoofing, or further network infiltration. The vulnerability affects organizations that rely on Avirt Mail for email services, creating exposure for email infrastructure that could serve as a foothold for broader network attacks. The attack vector requires minimal privileges as it operates over standard network protocols, making it particularly dangerous for email servers that are accessible from the internet. This weakness aligns with ATT&CK technique T1203, which describes the exploitation of software vulnerabilities to gain access to systems, and T1499, which covers the use of network denial of service attacks to disrupt services.
Mitigation strategies for CVE-2000-0971 require immediate implementation of several protective measures including patching the affected Avirt Mail installations to the latest available versions that address the buffer overflow conditions. Organizations should implement input validation mechanisms that enforce maximum length limits on SMTP command arguments, particularly for RCPT TO and MAIL FROM parameters. Network segmentation and access controls should be strengthened to limit exposure of vulnerable mail servers to untrusted networks. Additionally, implementing SMTP protocol filtering and monitoring systems can help detect and prevent exploitation attempts by identifying unusually long command sequences. The vulnerability demonstrates the importance of proper input validation and buffer management in network services, emphasizing the need for security practices such as those outlined in the OWASP Top Ten and NIST Cybersecurity Framework. Regular security assessments and vulnerability scanning should be conducted to identify similar weaknesses in other network services and applications that may be susceptible to similar buffer overflow exploitation techniques.