CVE-2001-1078 in eXtremail
Summary
by MITRE
Format string vulnerability in flog function of eXtremail 1.1.9 and earlier allows remote attackers to gain root privileges via format specifiers in the SMTP commands (1) HELO, (2) EHLO, (3) MAIL FROM, or (4) RCPT TO, and the POP3 commands (5) USER and (6) other commands that can be executed after POP3 authentication.
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Analysis
by VulDB Data Team • 09/29/2025
The vulnerability described in CVE-2001-1078 represents a critical format string flaw within the eXtremail email server software version 1.1.9 and earlier. This security weakness exists in the flog function which processes incoming SMTP and POP3 commands from remote clients. The flaw allows malicious actors to exploit the application's handling of format specifiers in email protocol commands, potentially enabling privilege escalation to root level access on the affected system. The vulnerability specifically targets six distinct command sequences that can be executed during SMTP and POP3 sessions, making it particularly dangerous as it affects both incoming and outgoing email processing capabilities.
The technical implementation of this vulnerability stems from improper input validation within the flog function that handles logging operations for various email protocol commands. When the eXtremail server receives commands such as HELO, EHLO, MAIL FROM, RCPT TO, USER, or other authenticated POP3 commands, it processes the user-supplied data without adequate sanitization. The format string vulnerability occurs because the application directly uses user-controllable input as format specifiers in printf-style functions, without proper escaping or validation. This creates opportunities for attackers to inject malicious format specifiers that can manipulate the program's memory layout, potentially leading to stack corruption and arbitrary code execution.
From an operational perspective, this vulnerability presents a severe threat to email server security as it allows remote attackers to execute arbitrary code with the privileges of the eXtremail process, which typically runs with root privileges on Unix-like systems. The attack vector is particularly concerning because it can be exploited during normal email protocol operations without requiring authentication for the initial exploitation phase. The vulnerability affects both SMTP and POP3 protocols, meaning that attackers can leverage it through multiple email communication channels. This makes the exploitation more likely to succeed in real-world scenarios where email servers typically handle numerous connections from various sources.
The impact of this vulnerability extends beyond simple privilege escalation as it can enable complete system compromise and persistent access to the affected infrastructure. Attackers can potentially use this vulnerability to install backdoors, exfiltrate sensitive data, or establish persistent command and control channels. The vulnerability aligns with CWE-134 which specifically addresses format string vulnerabilities where format strings are constructed from user-supplied data, and it maps to ATT&CK technique T1059 for command and scripting interpreter usage. Organizations running vulnerable eXtremail versions face significant risk of data breaches and system compromise, particularly in environments where email servers are exposed to untrusted networks or where the servers handle sensitive communications.
Mitigation strategies for CVE-2001-1078 require immediate patching of the eXtremail software to version 1.1.10 or later, which contains the necessary fixes for the format string vulnerability. System administrators should also implement network segmentation to limit access to email servers and deploy intrusion detection systems to monitor for exploitation attempts. Additional protective measures include disabling unnecessary email protocols, implementing strict input validation at network boundaries, and conducting regular security audits of email infrastructure. The vulnerability serves as a reminder of the critical importance of proper input validation and secure coding practices in network services, particularly those handling user-controllable data in protocol implementations. Organizations should also consider implementing application-level firewalls and monitoring for unusual command sequences that might indicate exploitation attempts against similar vulnerabilities.