CVE-2017-8438 in X-Pack Security
Summary
by MITRE
Elastic X-Pack Security versions 5.0.0 to 5.4.0 contain a privilege escalation bug in the run_as functionality. This bug prevents transitioning into the specified user specified in a run_as request. If a role has been created using a template that contains the _user properties, the behavior of run_as will be incorrect. Additionally if the run_as user specified does not exist, the transition will not happen.
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Analysis
by VulDB Data Team • 10/13/2019
The vulnerability identified as CVE-2017-8438 affects Elastic X-Pack Security versions 5.0.0 through 5.4.0 and represents a critical privilege escalation flaw within the run_as functionality. This issue specifically targets the authorization mechanisms that allow users to execute operations on behalf of other users, a feature commonly used in enterprise security systems to delegate administrative tasks while maintaining audit trails. The vulnerability stems from improper handling of user transitions within the role-based access control system, creating a scenario where legitimate security controls fail to function as intended. The flaw manifests when roles are configured with templates containing _user properties, which are essential components for defining user identity mappings in the Elastic security framework.
The technical implementation of this vulnerability involves a fundamental breakdown in the run_as request processing logic. When a user attempts to transition to a specified run_as user through a role configuration, the system fails to properly validate or execute the transition under specific conditions. This failure occurs particularly when roles utilize templates that incorporate _user properties, which are designed to dynamically map user identities during authorization processes. The vulnerability creates a situation where the system either refuses to transition to the specified user or fails to properly authenticate the transition, effectively bypassing intended access controls. This malfunction represents a direct violation of the principle of least privilege and can potentially allow unauthorized users to escalate their privileges within the Elastic security domain.
The operational impact of CVE-2017-8438 extends beyond simple access control bypasses and can significantly compromise the security posture of organizations relying on Elastic X-Pack for log management and security monitoring. Attackers who can exploit this vulnerability may gain unauthorized access to sensitive data, administrative functions, or other users' privileges within the Elastic cluster. The vulnerability's presence in versions 5.0.0 through 5.4.0 means that organizations running these specific releases face a substantial risk, particularly in environments where run_as functionality is actively used for operational tasks. This flaw directly contradicts the security expectations of enterprise users who depend on robust access controls to protect their data and systems. The vulnerability's potential for privilege escalation makes it particularly dangerous as it could enable attackers to move laterally within the Elastic ecosystem or access sensitive monitoring data that should remain restricted.
Organizations should immediately implement mitigations by upgrading to Elastic X-Pack Security versions 5.4.1 or later, where this vulnerability has been addressed through proper handling of run_as transitions and enhanced validation of user identity mappings. The fix involves correcting the processing logic for roles that contain _user properties in their templates, ensuring that legitimate run_as requests are properly executed while maintaining appropriate security controls. Security teams should also conduct comprehensive audits of existing role configurations to identify and remediate any templates that might be vulnerable to this issue. The vulnerability aligns with CWE-284, which addresses improper access control, and could be categorized under ATT&CK technique T1078 for valid accounts and privilege escalation. Additionally, this flaw demonstrates the importance of proper input validation and access control implementation in distributed security systems, highlighting how seemingly minor configuration issues can create significant security risks in enterprise monitoring platforms.