CVE-2005-2069 in pam_ldap
Summary
by MITRE
pam_ldap and nss_ldap, when used with OpenLDAP and connecting to a slave using TLS, does not use TLS for the subsequent connection if the client is referred to a master, which may cause a password to be sent in cleartext and allows remote attackers to sniff the password.
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Analysis
by VulDB Data Team • 03/11/2021
The vulnerability described in CVE-2005-2069 affects the Lightweight Directory Access Protocol authentication and name service modules pam_ldap and nss_ldap when integrated with OpenLDAP systems. This flaw manifests specifically when clients connect to LDAP slave servers using Transport Layer Security but encounter a referral to a master server during the authentication process. The issue stems from improper TLS handling during the referral resolution phase, creating a security gap that can result in credential exposure.
The technical implementation flaw occurs in the LDAP client-side libraries where the system fails to maintain the established TLS connection context when processing server referrals. When a slave server responds to an authentication request with a referral to a master server, the pam_ldap and nss_ldap modules do not automatically establish a new TLS connection to the master server. This behavior violates the principle of secure communication continuity and creates an attack surface where sensitive authentication data can be transmitted in cleartext over the network.
The operational impact of this vulnerability is significant for organizations relying on LDAP-based authentication systems. Remote attackers positioned within network traffic can intercept and sniff authentication credentials, particularly passwords, during the referral process. This weakness directly violates the security requirements outlined in the OpenLDAP documentation and compromises the fundamental security guarantees that TLS encryption is designed to provide. The vulnerability affects systems where LDAP referrals are commonly used, which is standard practice in distributed directory environments.
This vulnerability maps to CWE-310 in the Common Weakness Enumeration, specifically addressing cryptographic issues related to improper use of TLS and the lack of secure communication channel maintenance. From an adversary perspective, this represents a medium to high severity threat that aligns with ATT&CK technique T1552.001 for unsecured credentials and T1046 for network service discovery. The attack vector requires network access to observe traffic, making it particularly concerning in environments where attackers may have access to network segments or can perform man-in-the-middle attacks.
Organizations should implement immediate mitigations including ensuring all LDAP servers in a referral chain maintain consistent TLS configurations, updating to patched versions of pam_ldap and nss_ldap modules, and implementing network monitoring to detect unauthorized cleartext transmissions. System administrators should verify that all LDAP referrals are processed through secure channels and consider implementing additional authentication mechanisms such as Kerberos or certificate-based authentication to reduce reliance on simple password exchanges. The vulnerability highlights the importance of proper security context preservation in distributed authentication systems and underscores the need for comprehensive testing of referral handling in security-critical applications.