CVE-2013-4223 in Linux
Summary
by MITRE
The Gentoo Nullmailer package before 1.11-r2 uses world-readable permissions for /etc/nullmailer/remotes, which allows local users to obtain SMTP authentication credentials by reading the file.
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Analysis
by VulDB Data Team • 03/21/2019
The vulnerability identified as CVE-2013-4223 affects the Gentoo Nullmailer package version 1.11-r2 and earlier, presenting a critical security flaw in file permission management. This issue stems from the package's improper configuration of file permissions for the /etc/nullmailer/remotes file, which is designed to store SMTP authentication credentials for email relay configuration. The flaw represents a direct violation of the principle of least privilege and demonstrates poor access control implementation within the mail delivery system.
The technical root cause of this vulnerability lies in the package's default installation process failing to set appropriate file permissions for the remotes configuration file. Specifically, the file is created with world-readable permissions, meaning any local user on the system can access and read its contents without authentication. This misconfiguration allows attackers with local access to extract sensitive SMTP credentials that are typically stored in this file for authenticating with remote mail servers. The vulnerability is classified as a privilege escalation issue under CWE-276, specifically related to incorrect permissions for a resource, and falls under the broader category of insecure configuration management.
The operational impact of this vulnerability extends beyond simple credential exposure, as it provides attackers with the means to potentially compromise the entire email relay infrastructure. Once credentials are obtained, malicious actors can send spam emails, relay messages through the compromised system, or use the credentials for further attacks against other systems. The vulnerability is particularly concerning in multi-user environments where local access might be more easily obtained through various attack vectors such as social engineering, compromised user accounts, or other system weaknesses. According to ATT&CK framework, this represents a technique for Credential Access (T1566) through the exploitation of weak file permissions and privilege escalation (T1548).
Mitigation strategies for this vulnerability include immediate manual correction of file permissions by setting restrictive access controls on the /etc/nullmailer/remotes file, typically to user-only read/write permissions. The recommended fix involves changing ownership and permissions to ensure only the intended system processes can access the credentials. System administrators should also implement regular security audits to verify proper file permissions across all configuration files. Additionally, upgrading to Gentoo Nullmailer package version 1.11-r2 or later resolves the issue through proper implementation of secure default configurations. Organizations should consider implementing automated monitoring tools to detect and alert on improper file permissions, as this vulnerability highlights the importance of maintaining proper access controls for sensitive configuration data. The fix aligns with security best practices outlined in various compliance frameworks including NIST SP 800-53 and ISO 27001, which emphasize the importance of proper access control and secure configuration management.