CVE-2018-6333 in Nuclide
Summary
by MITRE
The hhvm-attach deep link handler in Nuclide did not properly sanitize the provided hostname parameter when rendering. As a result, a malicious URL could be used to render HTML and other content inside of the editor's context, which could potentially be chained to lead to code execution. This issue affected Nuclide prior to v0.290.0.
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Analysis
by VulDB Data Team • 05/06/2025
The vulnerability identified as CVE-2018-6333 resides within the hhvm-attach deep link handler component of the Nuclide development environment, which is part of Facebook's Hack programming language ecosystem. This flaw represents a classic cross-site scripting vulnerability that exploits improper input validation mechanisms within the editor's deep link processing functionality. The vulnerability specifically affects the Nuclide IDE prior to version 0.290.0, indicating that this was a known issue that required a specific version update to remediate properly. The deep link handler in question processes URLs that contain hostname parameters, which are intended to facilitate direct access to specific debugging or development targets within the HHVM runtime environment.
The technical implementation of this vulnerability stems from inadequate sanitization of user-provided hostname parameters within the Nuclide editor's rendering pipeline. When a malicious URL is processed through the hhvm-attach handler, the system fails to properly escape or validate the hostname input before incorporating it into the HTML rendering context. This omission creates a condition where arbitrary HTML content can be injected directly into the editor's display area, effectively bypassing the normal security boundaries that should separate user input from the rendering environment. The vulnerability operates at the intersection of input validation and output encoding, where the system assumes that user-provided parameters are safe without implementing proper sanitization measures.
The operational impact of this vulnerability extends beyond simple cross-site scripting, as it provides a potential attack vector for more sophisticated exploitation techniques. An attacker who can craft a malicious URL and convince a victim to open it within the Nuclide editor could execute arbitrary HTML content within the editor's context, potentially leading to further privilege escalation or code execution. This vulnerability particularly affects developers working in environments where Nuclide is used for Hack language development, as the editor's deep link functionality is commonly used for debugging and development workflows. The attack surface is amplified by the fact that developers often trust URLs from various sources, making social engineering a potential delivery mechanism for this exploit.
The remediation for this vulnerability requires implementing proper input sanitization and output encoding mechanisms within the Nuclide editor's deep link handler. This involves ensuring that all hostname parameters are properly escaped before being rendered within the HTML context, and that the system validates input parameters against expected formats and ranges. The fix implemented in Nuclide version 0.290.0 demonstrates the importance of input validation and proper security hygiene in development tools, as these environments often contain sensitive code and debugging information that makes them attractive targets for attackers. Organizations should consider implementing automated security testing for development environments and ensuring that all third-party components are regularly updated to address known vulnerabilities.
This vulnerability aligns with CWE-79, which describes cross-site scripting flaws that occur when untrusted data is sent to a web browser without proper validation or sanitization. The ATT&CK framework would categorize this under T1203, which covers exploitation of remote services, as the vulnerability enables attackers to exploit the development environment's functionality to execute malicious code. The issue also demonstrates the broader security challenge of securing development tools, which often operate with elevated privileges and access to sensitive code repositories, making them prime targets for supply chain attacks. Proper security controls should include regular vulnerability assessments of development environments and ensuring that all components maintain current security patches.