CVE-2017-8445 in TLS Trust Manager
Summary
by MITRE
An error was found in the X-Pack Security TLS trust manager for versions 5.0.0 to 5.5.1. If reloading the trust material fails the trust manager will be replaced with an instance that trusts all certificates. This could allow any node using any certificate to join a cluster. The proper behavior in this instance is for the TLS trust manager to deny all certificates.
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Analysis
by VulDB Data Team • 11/09/2019
The vulnerability identified as CVE-2017-8445 resides within the X-Pack Security TLS trust manager implementation of the elastic stack versions 5.0.0 through 5.5.1. This flaw represents a critical security oversight in the certificate validation process that governs cluster node communication and authentication. The vulnerability manifests when the system attempts to reload trust material for TLS connections but encounters a failure during this process. The improper handling of this failure condition creates a dangerous security boundary where the system transitions from a secure state to an insecure one, fundamentally compromising the integrity of the cluster's trust model.
The technical flaw operates through a flawed error handling mechanism within the TLS trust manager component. When the trust material reloading process fails, the system should maintain strict certificate validation policies and deny all certificates rather than falling back to a permissive trust model. Instead, the implementation replaces the trust manager with an instance that trusts all certificates, effectively nullifying the entire TLS security framework. This behavior creates an authentication bypass vulnerability that allows any unauthorized node to present any certificate and successfully join the cluster, regardless of the certificate's validity or trust chain. The flaw directly violates the fundamental principles of certificate-based authentication and cluster security that are essential for maintaining data integrity and preventing unauthorized access.
The operational impact of this vulnerability extends far beyond simple authentication bypass. An attacker who gains the ability to trigger the trust material reloading failure could potentially compromise entire elastic clusters by introducing malicious nodes that appear legitimate to the cluster's security mechanisms. This vulnerability undermines the core security model of distributed systems by allowing unauthorized entities to establish trust relationships with the cluster. The implications are particularly severe in environments where elastic clusters handle sensitive data, as this vulnerability could enable data exfiltration, privilege escalation, or complete cluster takeover. The vulnerability affects all nodes within the cluster that rely on the X-Pack Security TLS trust manager, making it a systemic risk rather than an isolated component failure.
The vulnerability maps directly to CWE-295 which describes improper certificate validation, and aligns with ATT&CK technique T1566 related to credential harvesting and T1071 for application layer protocol usage. Organizations affected by this vulnerability should immediately upgrade to versions of elastic stack that contain the patch for this issue, specifically versions 5.5.2 and later where the proper error handling has been implemented. The recommended mitigation involves not only applying the software patch but also implementing additional monitoring for trust material reload events and ensuring that certificate management processes are robust enough to prevent the conditions that trigger this vulnerability. Security teams should also conduct thorough assessments of their elastic cluster configurations to identify any nodes that might be vulnerable to this specific TLS trust manager behavior and implement additional controls to prevent unauthorized node addition to the cluster.