CVE-2013-6171 in Dovecot
Summary
by MITRE
checkpassword-reply in Dovecot before 2.2.7 performs setuid operations to a user who is authenticating, which allows local users to bypass authentication and access virtual email accounts by attaching to the process and using a restricted file descriptor to modify account information in the response to the dovecot-auth server.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 01/11/2022
The vulnerability identified as CVE-2013-6171 resides within the Dovecot email server software's authentication mechanism, specifically affecting versions prior to 2.2.7. This flaw represents a critical security weakness that exploits the way Dovecot handles authentication processes and setuid operations during user verification. The vulnerability occurs within the checkpassword-reply component, which is responsible for processing authentication responses from external authentication programs. The issue manifests when Dovecot performs setuid operations to the user attempting to authenticate, creating an exploitable condition that can be leveraged by local attackers.
The technical flaw stems from improper privilege management during the authentication process where Dovecot executes setuid operations on behalf of the authenticating user. This creates a window of opportunity for malicious local users to attach to the running process and manipulate file descriptors to modify authentication responses. The vulnerability is particularly dangerous because it allows attackers to bypass the normal authentication mechanisms entirely, gaining unauthorized access to virtual email accounts without proper credentials. The restricted file descriptor manipulation enables attackers to alter the authentication response data that is sent back to the dovecot-auth server, effectively impersonating legitimate users.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it fundamentally undermines the security model of virtual email account management. Attackers can exploit this flaw to gain access to any virtual email account hosted on the affected Dovecot server, potentially compromising sensitive email communications and user data. The vulnerability is particularly concerning in multi-tenant email environments where multiple users share the same server infrastructure, as it could enable lateral movement and data exfiltration across different user accounts. Organizations relying on Dovecot for email services face significant risk of unauthorized access to their email infrastructure, potentially leading to data breaches, spam relay abuse, and other malicious activities.
Mitigation strategies for CVE-2013-6171 primarily focus on upgrading to Dovecot version 2.2.7 or later, which includes patches addressing the privilege escalation issue in the checkpassword-reply component. System administrators should also implement additional security controls such as restricting local user access to authentication processes, monitoring for unauthorized process attachment attempts, and implementing proper file descriptor access controls. The vulnerability aligns with CWE-276, which covers improper privilege management, and can be mapped to ATT&CK technique T1078.1.1 for valid accounts and T1566 for social engineering attacks that leverage authentication bypasses. Organizations should conduct thorough security assessments of their email infrastructure to identify and remediate similar privilege escalation vulnerabilities, while also implementing robust logging and monitoring to detect potential exploitation attempts.