CVE-2009-3897 in Dovecot
Summary
by MITRE
Dovecot 1.2.x before 1.2.8 sets 0777 permissions during creation of certain directories at installation time, which allows local users to access arbitrary user accounts by replacing the auth socket, related to the parent directories of the base_dir directory, and possibly the base_dir directory itself.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 08/28/2021
The vulnerability described in CVE-2009-3897 represents a critical security flaw in Dovecot email server versions 1.2.x prior to 1.2.8. This issue stems from improper permission handling during the installation process where the software creates certain directories with overly permissive 0777 permissions. The flaw exists within the installation and initialization routines of the email server, specifically affecting how the system manages directory creation and access controls. The vulnerability is particularly concerning because it directly impacts the authentication mechanism of the email server, creating potential entry points for local attackers to compromise user accounts.
The technical implementation of this vulnerability involves the creation of directories with world-readable, world-writable, and world-executable permissions during installation. When Dovecot initializes, it creates parent directories of the base_dir configuration parameter with 0777 permissions, which means any local user on the system can read, write, and execute files within these directories. This permission structure creates a dangerous situation where an attacker can replace the authentication socket file, effectively hijacking the authentication process. The authentication socket serves as a critical communication channel between the mail server and its authentication modules, making it a prime target for privilege escalation attacks.
The operational impact of this vulnerability extends beyond simple local privilege escalation, as it enables attackers to gain access to arbitrary user accounts on the system. By replacing the auth socket, an attacker can potentially impersonate any user account that Dovecot manages, leading to unauthorized email access, data exfiltration, and potential further compromise of the system. This vulnerability particularly affects systems where Dovecot is used as an email server and where local users might have access to the system. The attack vector is relatively straightforward since it requires only local access and knowledge of the installation structure, making it a significant concern for system administrators who may not properly secure their email server installations.
The underlying cause of this vulnerability can be classified under CWE-732, which deals with Incorrect Permission Assignment for Critical Resource, and CWE-276, which addresses Incorrect Permission Assignment. From an attack perspective, this vulnerability aligns with techniques described in the MITRE ATT&CK framework under T1068, which covers Local Port Forwarding, and T1548.001, which covers Abuse of Functionality. The vulnerability demonstrates a classic case of insecure default permissions in system installation processes, where security considerations were not properly implemented during the software deployment phase.
Mitigation strategies for this vulnerability involve immediate patching of Dovecot installations to version 1.2.8 or later, which properly handles directory permissions during installation. System administrators should also conduct thorough audits of existing Dovecot installations to verify that no directories were created with incorrect permissions during the vulnerable version's installation process. Additionally, implementing proper access controls and monitoring for unauthorized modifications to authentication-related files can help detect potential exploitation attempts. Regular security assessments of email server configurations, combined with proper privilege separation and least-privilege principles, will help prevent similar issues from occurring in other system components. Organizations should also consider implementing automated security scanning tools that can identify insecure permission settings in critical system directories.