CVE-2015-0138 in Tivoli Directory Server
Summary
by MITRE
GSKit in IBM Tivoli Directory Server (ITDS) 6.0 before 6.0.0.73-ISS-ITDS-IF0073, 6.1 before 6.1.0.66-ISS-ITDS-IF0066, 6.2 before 6.2.0.42-ISS-ITDS-IF0042, and 6.3 before 6.3.0.35-ISS-ITDS-IF0035 and IBM Security Directory Server (ISDS) 6.3.1 before 6.3.1.9-ISS-ISDS-IF0009 does not properly restrict TLS state transitions, which makes it easier for remote attackers to conduct cipher-downgrade attacks to EXPORT_RSA ciphers via crafted TLS traffic, related to the "FREAK" issue, a different vulnerability than CVE-2015-0204.
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Analysis
by VulDB Data Team • 05/01/2022
The vulnerability described in CVE-2015-0138 represents a critical weakness in the cryptographic implementation of IBM Tivoli Directory Server and IBM Security Directory Server products. This flaw specifically affects the GSKit component responsible for handling TLS protocol communications within these directory services. The vulnerability stems from improper restrictions on TLS state transitions, creating a pathway for attackers to manipulate the cryptographic negotiation process during SSL/TLS handshakes. The issue directly relates to the FREAK (Factoring RSA Export Keys) vulnerability family, which exploits weaknesses in how systems handle weak cryptographic ciphers, particularly those that were historically restricted for export purposes but could be exploited by attackers to downgrade security levels.
The technical implementation flaw occurs when the TLS handshake process fails to properly validate or restrict state transitions between different cryptographic protocols and cipher suites. This allows remote attackers to craft malicious TLS traffic that forces the server to negotiate and use EXPORT_RSA ciphers, which are significantly weaker than the standard cryptographic algorithms that should be available. The vulnerability specifically targets the TLS protocol's ability to maintain secure cryptographic negotiations, enabling attackers to perform cipher-downgrade attacks that effectively weaken the security of communications. This weakness is particularly dangerous because it allows attackers to bypass normal security controls and force the system into using cryptographically weak cipher suites that are vulnerable to various attacks, including those that can be executed with relatively modest computational resources.
The operational impact of this vulnerability is substantial, as it provides attackers with a means to compromise the confidentiality and integrity of communications within directory services environments. Organizations using affected versions of IBM Tivoli Directory Server or IBM Security Directory Server face increased risk of man-in-the-middle attacks, where attackers can intercept and potentially modify sensitive data transmitted through these services. The vulnerability affects multiple product versions and release streams, indicating a widespread issue that would require coordinated patching efforts across different software versions. This creates additional operational complexity for security teams who must identify all affected systems and apply patches across various product lines. The vulnerability's relationship to the FREAK attack vector means that organizations may be exposed to attacks that have been previously documented and exploited in other systems, making this a particularly concerning weakness in directory service infrastructure.
Mitigation strategies for CVE-2015-0138 primarily focus on applying the vendor-provided patches that address the TLS state transition restrictions in the GSKit component. Organizations should prioritize patching all affected versions of IBM Tivoli Directory Server and IBM Security Directory Server to ensure proper cryptographic negotiation and prevent forced cipher downgrades. Security teams should also implement network monitoring to detect anomalous TLS handshake patterns that might indicate attempted exploitation of this vulnerability. The mitigation approach aligns with CWE-327, which addresses weak cryptographic algorithms and improper implementation of cryptographic protocols, and follows ATT&CK technique T1566 related to credential access through network attacks. Additional defensive measures include configuring systems to disable weak cipher suites, implementing strict TLS protocol version enforcement, and conducting regular security assessments of cryptographic implementations within directory services infrastructure to identify similar vulnerabilities that might exist in other components of the security ecosystem.