CVE-2006-5659 in PAM_extern
Summary
by MITRE
PAM_extern before 0.2 sends a password as a command line argument, which allows local users to obtain the password by listing the command line arguments, such as ps. NOTE: the provenance of this information is unknown; the details are obtained solely from third party information.
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Analysis
by VulDB Data Team • 04/26/2026
The vulnerability identified as CVE-2006-5659 affects the PAM_extern module version 0.2 and earlier, representing a critical security flaw in authentication handling mechanisms. This issue stems from the module's improper implementation of password transmission during authentication processes, where passwords are inadvertently exposed through command line arguments. The flaw exists in the design and execution of the PAM_extern external authentication module, which fails to properly secure sensitive authentication data during its processing lifecycle.
The technical implementation of this vulnerability occurs when PAM_extern passes authentication credentials as command line parameters to external programs. This approach directly violates fundamental security principles for credential handling, as command line arguments are inherently visible to all processes on the system through various system monitoring tools. When the system executes authentication commands, the password becomes part of the process arguments that can be accessed by any user with appropriate permissions, making it trivial for local attackers to extract sensitive information through standard system utilities such as ps, top, or other process monitoring tools.
The operational impact of this vulnerability extends beyond simple credential exposure, as it fundamentally undermines the security model of authentication systems. Local users with minimal privileges can exploit this weakness to gain unauthorized access to authentication credentials, potentially leading to privilege escalation or lateral movement within compromised systems. The vulnerability affects systems where PAM_extern is configured as an authentication module, particularly in environments where multiple users share the same system and where process visibility is not properly restricted. This flaw demonstrates a classic security misconfiguration that violates the principle of least privilege and proper credential handling practices.
Security professionals should note that this vulnerability aligns with CWE-255, which addresses credentials management issues, and represents a specific implementation weakness in authentication modules. The attack vector described in the vulnerability maps to techniques found in the MITRE ATT&CK framework under T1003.001 for OS Credential Dumping, where adversaries attempt to access credentials through process memory or command line arguments. The exposure of passwords through command line arguments also relates to CWE-312, which covers exposure of sensitive information through improper output handling, and CWE-772, which addresses improper cleanup of sensitive data.
The recommended mitigation strategies include immediate upgrading to PAM_extern version 0.2 or later, which presumably contains the necessary security fixes to prevent credential exposure through command line arguments. System administrators should also implement process monitoring and restriction mechanisms to limit visibility of command line arguments for authentication processes. Additional protective measures include configuring proper access controls to prevent unauthorized users from accessing process information, implementing monitoring for suspicious process activity, and ensuring that authentication modules properly sanitize sensitive data during processing. Organizations should also conduct comprehensive audits of their PAM configurations to identify and remediate similar vulnerabilities across their authentication infrastructure.