CVE-2021-40089 in EJBCA
Summary
by MITRE • 08/25/2021
An issue was discovered in PrimeKey EJBCA before 7.6.0. The General Purpose Custom Publisher, which is normally run to invoke a local script upon a publishing operation, was still able to run if the System Configuration setting Enable External Script Access was disabled. With this setting disabled it's not possible to create new such publishers, but existing publishers would continue to run.
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Analysis
by VulDB Data Team • 08/29/2021
The vulnerability CVE-2021-40089 affects PrimeKey EJBCA versions prior to 7.6.0 and represents a significant security flaw in the system's privilege management and access control mechanisms. This issue specifically targets the General Purpose Custom Publisher functionality within the Enterprise Java Beans Certificate Authority platform, which is widely used for managing digital certificates in enterprise environments. The vulnerability manifests when the System Configuration setting Enable External Script Access is disabled, a security measure designed to prevent unauthorized script execution and limit potential attack surfaces. The flaw creates a privilege escalation scenario where previously configured publishers can continue executing local scripts even when the system has explicitly disabled the capability to create new such publishers, effectively bypassing the intended security controls.
The technical implementation of this vulnerability stems from a logic flaw in the access control validation process within EJBCA's configuration management system. When the Enable External Script Access setting is disabled, the system correctly prevents the creation of new General Purpose Custom Publishers, but fails to properly validate existing publisher configurations against this security restriction. This inconsistency creates a persistent execution path where legacy publisher configurations retain their ability to invoke local scripts, despite the system-wide policy that should have disabled such functionality. The vulnerability falls under CWE-693 Protection Mechanism Failure, as it represents a failure in the enforcement of security mechanisms that should have been uniformly applied across all publisher operations. This type of flaw commonly occurs in systems where access control checks are not consistently applied across all execution paths, particularly when legacy configurations are not properly validated against current security policies.
The operational impact of this vulnerability is substantial, particularly in enterprise environments where certificate management systems serve as critical infrastructure components. Attackers who can gain access to the EJBCA administrative interface or other privileged accounts could potentially exploit this vulnerability to execute arbitrary code on the system hosting the certificate authority. The ability to run local scripts through existing publishers creates multiple attack vectors including privilege escalation, data exfiltration, and system compromise. This vulnerability is particularly concerning because it operates silently within the existing security framework, making detection difficult and potentially allowing attackers to maintain persistent access. The flaw could enable attackers to escalate privileges, modify certificate issuance processes, or even gain complete system control through the execution of malicious scripts on the certificate authority server.
Mitigation strategies for CVE-2021-40089 should focus on immediate remediation and comprehensive security hardening. Organizations should immediately upgrade to PrimeKey EJBCA version 7.6.0 or later, which contains the necessary patches to address this vulnerability. System administrators should conduct thorough audits of existing General Purpose Custom Publishers to identify and disable any unnecessary or potentially compromised configurations. The recommended approach includes implementing strict access controls for certificate authority management interfaces, disabling external script access at the system level, and monitoring for unauthorized script execution. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and execution of malicious code through legitimate system tools, specifically T1059.007 for script execution and T1068 for local privilege escalation. Organizations should also implement network segmentation and monitoring solutions to detect anomalous script execution patterns that could indicate exploitation attempts. The vulnerability highlights the importance of comprehensive configuration management and the need for regular security assessments to identify inconsistencies between system policies and actual operational behavior.