CVE-2007-2173 in courier-imap
Summary
by MITRE
Eval injection vulnerability in (1) courier-imapd.indirect and (2) courier-pop3d.indirect in Courier-IMAP before 4.0.6-r2, and 4.1.x before 4.1.2-r1, on Gentoo Linux allows remote attackers to execute arbitrary commands via the XMAILDIR variable, related to the LOGINRUN variable.
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Analysis
by VulDB Data Team • 08/01/2019
This vulnerability exists in the Courier-IMAP and Courier-POP3 server implementations on Gentoo Linux systems, specifically affecting versions prior to 4.0.6-r2 and 4.1.2-r1 respectively. The flaw represents a critical eval injection vulnerability that occurs in the indirect execution paths of these mail server components, where user-supplied input is improperly processed and executed within the system's command execution context. The vulnerability manifests through the XMAILDIR variable, which is directly influenced by the LOGINRUN variable, creating a dangerous chain where attacker-controlled data can be interpreted and executed as shell commands.
The technical implementation of this vulnerability stems from insufficient input validation and sanitization within the mail server's authentication and session management routines. When users authenticate to the system, the LOGINRUN variable is set based on user input, which then gets passed to the XMAILDIR variable without proper escaping or filtering. This creates an environment where malicious input can be interpreted by the system's shell interpreter, allowing attackers to inject arbitrary commands that execute with the privileges of the mail server process. The vulnerability is classified as a command injection flaw, specifically aligning with CWE-77 and CWE-94 categories, which deal with improper neutralization of special elements used in OS commands and eval injection respectively.
The operational impact of this vulnerability is severe, as it provides remote attackers with arbitrary code execution capabilities on affected systems. An attacker could leverage this vulnerability to execute commands with the privileges of the mail server process, potentially leading to complete system compromise, data exfiltration, or further lateral movement within the network. The vulnerability affects mail server functionality across various network protocols, making it particularly dangerous as it can be exploited through multiple attack vectors. This represents a critical security weakness that could be exploited by attackers without requiring authentication for the specific attack vector, though authentication might be needed for initial access depending on system configuration.
The recommended mitigations include immediate patching of the affected Courier-IMAP and Courier-POP3 packages to versions 4.0.6-r2 and 4.1.2-r1 respectively, which contain the necessary fixes to prevent the eval injection vulnerability. System administrators should also implement network segmentation and access controls to limit exposure of mail server services to untrusted networks. Additional defensive measures include monitoring for unusual authentication patterns and command execution attempts, implementing proper input validation at all system interfaces, and conducting regular security audits of mail server configurations. Organizations should also consider implementing intrusion detection systems that can identify suspicious command execution patterns and network traffic that may indicate exploitation attempts. The vulnerability's classification under ATT&CK technique T1059.007 (Command and Scripting Interpreter: PowerShell) and T1068 (Exploitation for Privilege Escalation) highlights the need for comprehensive monitoring and response strategies to detect and prevent exploitation attempts.