CVE-2008-1668 in HP-UX
Summary
by MITRE
ftpd.c in (1) wu-ftpd 2.4.2 and (2) ftpd in HP HP-UX B.11.11 assigns uid 0 to the FTP client in certain operating-system misconfigurations in which PAM authentication can succeed even though no passwd entry is available for a user, which allows remote attackers to gain privileges, as demonstrated by a login attempt for an LDAP account when nsswitch.conf does not specify LDAP for passwd information.
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Analysis
by VulDB Data Team • 08/15/2019
The vulnerability described in CVE-2008-1668 represents a critical privilege escalation flaw in the wu-ftpd and HP-UX ftpd implementations that stems from improper handling of authentication failures within the PAM (Pluggable Authentication Modules) framework. This issue occurs when the operating system's name service switching configuration contains misconfigurations that allow PAM authentication to succeed even when no corresponding user account exists in the local passwd database, creating a dangerous scenario where unauthorized users can potentially gain root privileges.
The technical flaw manifests specifically in the ftpd.c component of wu-ftpd version 2.4.2 and the HP-UX ftpd implementation, where the software fails to properly validate authentication results when PAM succeeds but the user account does not exist in the local user database. When a user attempts to authenticate through FTP using an account that exists in an external directory service such as LDAP but is not present in the local passwd file, the system incorrectly assigns uid 0 (root) to the authenticated session, effectively granting full administrative privileges to any remote attacker who can successfully authenticate through the flawed PAM configuration.
This vulnerability operates at the intersection of multiple security domains and aligns with CWE-284 Access Control Issues and CWE-305 Authentication Issues, demonstrating how improper authentication handling can lead to privilege escalation. The attack vector is particularly concerning as it can be exploited remotely without requiring any special privileges or local access to the system, making it a significant threat in networked environments where FTP services are exposed to untrusted networks.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally undermines the security model of the affected systems. When combined with the specific misconfiguration mentioned in the CVE description involving nsswitch.conf not specifying LDAP for passwd information, attackers can leverage this flaw to establish persistent access to systems. This represents a classic example of how insecure defaults and misconfigured system services can create attack surfaces that allow for arbitrary code execution with root privileges, as documented in the MITRE ATT&CK framework under privilege escalation techniques.
The exploitation of this vulnerability requires attackers to identify systems with the specific misconfiguration where PAM authentication succeeds for non-existent users, typically involving LDAP authentication with incomplete name service switching configurations. Organizations running affected versions of wu-ftpd or HP-UX ftpd should immediately implement mitigations including updating to patched versions, correcting the nsswitch.conf configuration to properly handle passwd lookups, and ensuring that all authentication modules are properly configured to reject invalid user accounts. Additional protective measures include implementing network segmentation, disabling unnecessary FTP services, and conducting comprehensive security audits to identify systems with similar misconfigurations that could be vulnerable to similar privilege escalation attacks.