CVE-2018-17191 in NetBeans
Summary
by MITRE
Apache NetBeans (incubating) 9.0 NetBeans Proxy Auto-Configuration (PAC) interpretation is vulnerable for remote command execution (RCE). Using the nashorn script engine the environment of the javascript execution for the Proxy Auto-Configuration leaks privileged objects, that can be used to circumvent the execution limits. If a different script engine was used, no execution limits were in place. Both vectors allow remote code execution.
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Analysis
by VulDB Data Team • 04/25/2020
The vulnerability CVE-2018-17191 represents a critical remote code execution flaw in Apache NetBeans 9.0's Proxy Auto-Configuration (PAC) processing functionality. This issue stems from the improper handling of JavaScript execution within the nashorn script engine, which is utilized for interpreting PAC files. The flaw exists in the security boundaries that should normally prevent privileged operations from being executed within the sandboxed JavaScript environment. When a PAC file is processed, the system inadvertently exposes privileged objects to the JavaScript execution context, effectively breaking the isolation that should protect the underlying system from malicious code execution.
The technical root cause of this vulnerability lies in the nashorn JavaScript engine's implementation within the NetBeans environment, where it fails to properly restrict access to system resources and privileged objects. This flaw creates a path where attacker-controlled JavaScript code can access objects that provide direct system-level capabilities, including the ability to execute arbitrary commands on the host system. The vulnerability manifests when the system processes PAC files that contain malicious JavaScript code, which can then leverage the exposed privileged objects to perform unauthorized operations. This represents a classic sandbox escape scenario where the intended security boundaries are bypassed through improper object exposure.
The operational impact of CVE-2018-17191 is severe as it allows remote attackers to achieve complete system compromise without requiring any authentication or local access. An attacker can craft a malicious PAC file that, when processed by the vulnerable NetBeans instance, executes arbitrary commands on the target system with the privileges of the NetBeans process. This could result in data exfiltration, system modification, or further lateral movement within a network. The vulnerability affects any system running Apache NetBeans 9.0 that processes PAC files, making it particularly dangerous in enterprise environments where proxy configurations are commonly managed through automated systems.
The security implications align with CWE-254 and CWE-94, which address security weaknesses related to improper restriction of operations within a security boundary and code injection vulnerabilities respectively. This vulnerability also maps to ATT&CK technique T1059.007 for execution through JavaScript and T1068 for privilege escalation. Organizations should immediately apply the vendor-provided patches to address this issue, as the vulnerability exists in the core proxy handling functionality that is likely to be used in production environments. Additionally, network segmentation and monitoring for suspicious PAC file processing activities should be implemented as defensive measures. The fix typically involves restricting access to privileged objects within the JavaScript execution context and ensuring proper sandboxing of script execution environments to prevent unauthorized system access.