CVE-2018-16621 in Nexus Repository Manager
Summary
by MITRE
Sonatype Nexus Repository Manager before 3.14 allows Java Expression Language Injection.
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Analysis
by VulDB Data Team • 04/13/2020
The vulnerability CVE-2018-16621 represents a critical Java Expression Language (JEL) injection flaw in Sonatype Nexus Repository Manager versions prior to 3.14. This vulnerability exists within the repository manager's handling of user-supplied input that is processed through the Expression Language framework, creating a pathway for arbitrary code execution. The flaw stems from insufficient input validation and sanitization mechanisms that fail to properly escape or filter user-provided data before it is interpreted by the EL engine. Security researchers identified that when administrators or users interact with certain repository management features, maliciously crafted input can be passed directly into expression evaluation contexts without proper security controls.
The technical implementation of this vulnerability allows attackers to exploit the Expression Language processing capabilities by injecting malicious expressions that execute arbitrary Java code on the target system. The underlying cause aligns with CWE-94, which describes improper control of generation of code, specifically when user input is directly processed through expression evaluation mechanisms. Attackers can leverage this vulnerability to execute commands, access sensitive data, or compromise the entire repository infrastructure. The vulnerability is particularly dangerous because it can be exploited through various attack vectors including repository metadata manipulation, user interface inputs, or API endpoints that accept user-provided parameters.
Operational impact of this vulnerability extends beyond simple code execution to encompass complete system compromise and data breaches. Organizations using vulnerable versions of Nexus Repository Manager face significant risk of unauthorized access to their artifact repositories, which may contain proprietary software, configuration files, and other sensitive information. The vulnerability enables attackers to escalate privileges, install backdoors, or exfiltrate repository contents. From an ATT&CK framework perspective, this vulnerability maps to techniques such as T1059.007 for Java Expression Language injection and T1078 for valid accounts usage, as attackers can leverage legitimate administrative functions to maintain persistent access. The attack surface is particularly broad since repository managers are often centrally located within development environments and may be accessible to multiple user roles.
Mitigation strategies for CVE-2018-16621 require immediate remediation through patching to version 3.14 or later, which implements proper input validation and sanitization controls. Organizations should also implement network segmentation to limit access to repository manager instances, enforce strict access controls, and monitor for suspicious API usage patterns. Additional protective measures include disabling unnecessary repository features, implementing web application firewalls, and conducting regular security assessments of repository configurations. Security teams should also establish monitoring protocols to detect potential exploitation attempts through log analysis and anomaly detection systems. The vulnerability demonstrates the critical importance of proper input validation in enterprise software and highlights the need for continuous security testing of application frameworks that process user-supplied data through dynamic evaluation mechanisms.