CVE-2012-0726 in Tivoli Directory Server
Summary
by MITRE
The default configuration of TLS in IBM Tivoli Directory Server (TDS) 6.3 and earlier supports the (1) NULL-MD5 and (2) NULL-SHA ciphers, which allows remote attackers to trigger unencrypted communication via the TLS Handshake Protocol.
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Analysis
by VulDB Data Team • 03/24/2021
The vulnerability identified as CVE-2012-0726 affects IBM Tivoli Directory Server version 6.3 and earlier, presenting a critical security flaw in the default TLS configuration that compromises the integrity of encrypted communications. This issue stems from the inclusion of weak cipher suites that enable attackers to manipulate the TLS handshake process and force the system into using unencrypted connections. The vulnerability specifically targets the NULL-MD5 and NULL-SHA cipher suites, which are inherently insecure as they provide no encryption or authentication mechanisms. These cipher suites are particularly dangerous because they allow for downgrade attacks where an attacker can force the TLS negotiation to use these weak ciphers instead of stronger alternatives.
The technical implementation of this vulnerability exploits the TLS Handshake Protocol by leveraging the fact that the default TDS configuration includes cipher suites that do not properly validate the security level of the negotiated encryption. When a client attempts to establish a TLS connection with TDS, the server may accept connections using these NULL ciphers, effectively bypassing the encryption layer entirely. This creates a man-in-the-middle attack vector where attackers can intercept, modify, or steal sensitive directory information without detection. The flaw represents a fundamental breakdown in the cryptographic security model, as it allows attackers to establish communication channels that appear secure but provide no actual protection.
The operational impact of this vulnerability is severe for organizations relying on Tivoli Directory Server for authentication and directory services. Directory servers typically contain highly sensitive information including user credentials, access controls, and organizational data that forms the backbone of enterprise security infrastructure. When attackers can force unencrypted communication, they gain access to potentially all directory information, including user accounts, group memberships, and access permissions that could be used for lateral movement within the network. This vulnerability directly violates the principles of confidentiality and integrity as defined in the CIA triad, making it particularly dangerous for environments where directory services are used for authentication and authorization.
Organizations should immediately implement mitigations that involve disabling the NULL-MD5 and NULL-SHA cipher suites in the TDS configuration, ensuring that only strong encryption algorithms are accepted during TLS negotiation. The recommended approach includes configuring the server to explicitly reject weak cipher suites and enforcing the use of modern, secure cipher suites such as those based on AES encryption with strong key lengths. This vulnerability aligns with CWE-327, which addresses the use of weak cryptographic algorithms, and represents a clear violation of the NIST SP 800-52 guidelines for TLS configuration. From an ATT&CK framework perspective, this vulnerability maps to T1566.001 (Phishing with Malicious Attachment) and T1071.001 (Application Layer Protocol: Web Protocols) as attackers can exploit this weakness to conduct credential theft and network reconnaissance activities.
The remediation process requires careful consideration of backward compatibility, as disabling these weak cipher suites may impact legacy clients that cannot support stronger encryption. Organizations should conduct thorough testing of their client applications and update them to support modern TLS versions before implementing the security patches. Additionally, monitoring and logging should be enhanced to detect any attempts to establish connections using weak cipher suites, which can serve as indicators of potential exploitation attempts. The vulnerability demonstrates the critical importance of proper cryptographic configuration management and the necessity of regularly reviewing security settings to ensure that default configurations do not introduce exploitable weaknesses into enterprise infrastructure.