CVE-1999-0102 in SLmail
Summary
by MITRE
Buffer overflow in SLmail 3.x allows attackers to execute commands using a large FROM line.
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Analysis
by VulDB Data Team • 10/27/2025
The vulnerability identified as CVE-1999-0102 represents a critical buffer overflow flaw within SLmail version 3.x email server software that fundamentally compromises system security through improper input validation. This vulnerability specifically targets the handling of the FROM email header field, where attackers can exploit a malformed input sequence to trigger memory corruption. The buffer overflow occurs when the mail server processes an excessively long FROM line, causing the program to overwrite adjacent memory locations beyond the allocated buffer boundaries. This type of vulnerability falls under the Common Weakness Enumeration category CWE-121, which classifies buffer overflow conditions that occur when a program writes data beyond the bounds of a fixed-length buffer. The attack vector leverages the SMTP protocol's standard header processing mechanisms, making it particularly dangerous as it can be exploited through normal email transmission channels without requiring special privileges or authentication.
The operational impact of this vulnerability extends far beyond simple denial of service scenarios, as it provides attackers with the capability to execute arbitrary commands on the affected system with the privileges of the mail server process. When an attacker crafts a specially formatted email message containing an oversized FROM line, the buffer overflow can be manipulated to overwrite critical memory segments including return addresses and function pointers, enabling the execution of malicious code within the target environment. This vulnerability directly maps to the MITRE ATT&CK framework's technique T1059.007 for command and scripting interpreter, where adversaries leverage compromised systems to execute commands through legitimate system interfaces. The attack typically follows a pattern where the attacker sends an email with a FROM header exceeding the buffer capacity, causing a stack-based buffer overflow that can be exploited to gain remote code execution. The severity of this vulnerability is amplified by the fact that SLmail servers often run with elevated privileges to handle email processing, potentially allowing attackers to achieve system-level compromise.
Mitigation strategies for CVE-1999-0102 must address both immediate defensive measures and long-term architectural improvements to prevent similar vulnerabilities from occurring in modern systems. Organizations should implement immediate patching procedures to upgrade to SLmail versions that properly validate input lengths and implement proper buffer management techniques, as this vulnerability was specifically addressed in subsequent releases. Network-level defenses should include SMTP header length restrictions and email filtering rules that can identify and block suspiciously long FROM lines before they reach the mail server. The implementation of stack canaries, address space layout randomization, and non-executable stack protections can provide additional layers of defense against exploitation attempts. Security monitoring should focus on unusual email traffic patterns and potential buffer overflow indicators in system logs. Additionally, regular security assessments should verify that all email server components properly implement input validation and that buffer management follows secure coding practices aligned with industry standards such as those outlined in the CERT/CC secure coding guidelines. The vulnerability serves as a historical example of how inadequate input validation in network services can create severe security implications that persist across multiple system components and attack vectors.