CVE-2019-18213 in XML Language Support
Summary
by MITRE
XML Language Server (aka lsp4xml) before 0.9.1, as used in Red Hat XML Language Support (aka vscode-xml) before 0.9.1 for Visual Studio and other products, allows XXE via a crafted XML document, with resultant SSRF (as well as SMB connection initiation that can lead to NetNTLM challenge/response capture for password cracking). This occurs in extensions/contentmodel/participants/diagnostics/LSPXMLParserConfiguration.java.
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Analysis
by VulDB Data Team • 01/27/2024
The vulnerability CVE-2019-18213 represents a critical security flaw in the XML Language Server (lsp4xml) component that affects Red Hat XML Language Support for Visual Studio Code and similar products. This issue stems from inadequate input validation and processing of XML documents within the language server's configuration parsing mechanism. The vulnerability exists specifically in the file extensions/contentmodel/participants/diagnostics/LSPXMLParserConfiguration.java, which handles XML document parsing operations. The flaw enables attackers to exploit XML External Entity (XXE) processing capabilities through maliciously crafted XML documents that can be loaded into the editor environment.
The technical implementation of this vulnerability allows for Server-Side Request Forgery (SSRF) attacks, where an attacker can manipulate the XML parser to make unauthorized network requests from the server hosting the language server. This occurs because the parser fails to properly sanitize external entity declarations and references within XML documents. Additionally, the vulnerability enables SMB connection initiation, which can capture NetNTLM challenge/response hashes that are subsequently vulnerable to password cracking attacks. This dual nature of the vulnerability makes it particularly dangerous as it can be exploited for both network reconnaissance and credential harvesting purposes.
From an operational impact perspective, this vulnerability affects developers who rely on XML language support features in their development environments. When a user opens a malicious XML file, the language server automatically processes it through the vulnerable parser, potentially exposing the development environment to external network access and credential compromise. The vulnerability is particularly concerning in enterprise environments where developers may encounter untrusted XML content from various sources, including third-party libraries, configuration files, or collaborative development platforms. The SSRF capability allows attackers to potentially access internal services that would otherwise be protected by network segmentation, while the SMB connection initiation enables passive credential harvesting attacks that can be used to break authentication systems.
The vulnerability aligns with CWE-611 (Improper Restriction of XML External Entity Reference) and can be mapped to ATT&CK technique T1190 (Exploit Public-Facing Application) and T1110 (Brute Force) within the MITRE ATT&CK framework. Organizations should implement immediate mitigations including updating to version 0.9.1 or later of the affected components, implementing network segmentation to restrict outbound connections from development environments, and monitoring for suspicious network activity that might indicate SSRF attempts. Additionally, developers should be educated about the risks of opening untrusted XML files and organizations should consider implementing content filtering solutions to prevent malicious XML content from being processed by language servers. The vulnerability demonstrates the importance of secure XML processing practices and highlights the need for proper input sanitization in language server implementations that handle untrusted data sources.