CVE-2005-3532 in Courier Mail Server
Summary
by MITRE
authpam.c in courier-authdaemon for Courier Mail Server 0.37.3 through 0.52.1, when using pam_tally, does not call the pam_acct_mgmt function to verify that access should be granted, which allows attackers to authenticate to the server using accounts that have been disabled.
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Analysis
by VulDB Data Team • 07/06/2021
The vulnerability described in CVE-2005-3532 affects the courier-authdaemon component of the Courier Mail Server, specifically within the authpam.c module. This issue exists in versions ranging from 0.37.3 through 0.52.1 and represents a critical authentication flaw that undermines the security controls implemented through the Pluggable Authentication Modules (PAM) framework. The vulnerability stems from an incomplete implementation of the PAM authentication flow where the system fails to properly validate account status during the authentication process.
The technical flaw manifests when the courier-authdaemon utilizes pam_tally for authentication purposes but omits the crucial call to pam_acct_mgmt function. This function is responsible for verifying that the account is still active and has not been disabled due to security policies, failed login attempts, or administrative actions. Without this verification step, the authentication system accepts credentials even when the target account has been administratively disabled or locked out through account lockout mechanisms. This represents a direct violation of the principle of least privilege and authentication integrity.
The operational impact of this vulnerability is significant as it allows unauthorized access to mail server resources through disabled accounts. Attackers can exploit this weakness to gain access to mailboxes, send emails, or perform other malicious activities using accounts that should no longer be functional. This vulnerability particularly affects environments where account lockout policies are implemented to prevent brute force attacks or where administrative controls have disabled compromised accounts. The flaw essentially bypasses account status checks that are fundamental to maintaining secure authentication systems.
From a cybersecurity perspective, this vulnerability aligns with CWE-610, which describes "Remote Reference to a Resource Not Owned by the User" and CWE-287, which addresses "Improper Authentication." The attack vector follows patterns described in the MITRE ATT&CK framework under T1110, specifically "Brute Force" and "Credential Access" techniques where attackers leverage disabled accounts to maintain persistence or gain unauthorized access. Organizations using vulnerable versions of Courier Mail Server face increased risk of unauthorized access, data breaches, and potential compromise of email infrastructure.
The recommended mitigation strategy involves upgrading to a patched version of courier-authdaemon where the pam_acct_mgmt function is properly implemented and called during the authentication process. System administrators should also review and enforce proper account management policies, including timely disabling of compromised accounts and implementing additional authentication controls such as multi-factor authentication. Additionally, monitoring for unusual authentication patterns and implementing proper account lockout mechanisms with appropriate time-based resets can help detect and prevent exploitation of this vulnerability. Organizations should conduct comprehensive security assessments of their email infrastructure to identify and remediate similar authentication bypass vulnerabilities that may exist in other components of their mail server implementations.