CVE-2019-0728 in Visual Studio Code
Summary
by MITRE
A remote code execution vulnerability exists in Visual Studio Code when it process environment variables after opening a project, aka 'Visual Studio Code Remote Code Execution Vulnerability'.
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Analysis
by VulDB Data Team • 07/10/2023
The CVE-2019-0728 vulnerability represents a critical remote code execution flaw in Microsoft Visual Studio Code that manifests when the IDE processes environment variables following project opening. This vulnerability specifically affects the remote development capabilities of Visual Studio Code, particularly the VS Code Remote - SSH extension that enables developers to work on remote machines through secure shell connections. The flaw resides in how Visual Studio Code handles environment variable parsing and execution within the remote development context, creating a pathway for malicious actors to execute arbitrary code on targeted systems. The vulnerability impacts users who have the VS Code Remote - SSH extension installed and are connecting to remote servers, making it particularly concerning for enterprise environments where remote development is prevalent. Security researchers identified that the vulnerability stems from improper input validation and sanitization of environment variables that are processed during the remote development session initialization phase. This issue enables attackers to manipulate environment variable values in ways that can lead to arbitrary code execution, potentially compromising the entire development environment and underlying systems.
The technical exploitation of CVE-2019-0728 occurs through manipulation of environment variables that Visual Studio Code processes during remote session establishment. When a developer opens a project through the remote SSH extension, the IDE reads and processes various environment variables from the remote system. The vulnerability arises because Visual Studio Code does not adequately sanitize these variables before using them in execution contexts, allowing attackers to inject malicious code through carefully crafted environment variable values. The flaw essentially allows attackers to escalate privileges and execute arbitrary commands on the remote system through the compromised Visual Studio Code process. This vulnerability is particularly dangerous because it leverages the trust relationship between the developer's local Visual Studio Code instance and the remote system, exploiting the legitimate remote development functionality to gain unauthorized access. The exploitation requires minimal user interaction beyond opening a project, making it particularly stealthy and difficult to detect. Attackers can craft environment variables that contain shell commands or malicious payloads, which are then executed by Visual Studio Code during the normal project opening process. This vulnerability aligns with CWE-78 Improper Neutralization of Special Elements used in an OS Command, as it involves the improper handling of environment variables that can be interpreted as commands by the underlying operating system.
The operational impact of CVE-2019-0728 extends beyond simple code execution to encompass complete system compromise and data exfiltration capabilities. Organizations using Visual Studio Code for remote development face significant risk of unauthorized access to their development environments, source code repositories, and sensitive infrastructure components. The vulnerability can be exploited to establish persistent access, escalate privileges, and potentially move laterally within network environments. Attackers can leverage this vulnerability to gain access to development credentials, API keys, and other sensitive information stored in environment variables or accessible through the compromised system. The remote nature of the attack means that exploitation can occur from anywhere on the internet without requiring physical access to the target system. This makes the vulnerability particularly attractive to threat actors targeting development environments, where sensitive data and access credentials are commonly stored. The impact is amplified in continuous integration/continuous deployment pipelines where Visual Studio Code might be used for configuration management and automated builds. Organizations with remote development practices are especially vulnerable, as the attack surface expands to include all systems accessible through SSH connections that are managed through Visual Studio Code. The vulnerability also affects the integrity of development workflows, potentially allowing attackers to inject malicious code into development processes or compromise the build environment.
Mitigation strategies for CVE-2019-0728 focus primarily on immediate software updates and operational security improvements. Microsoft released patches for Visual Studio Code that address the vulnerability by implementing proper sanitization and validation of environment variables during remote session initialization. Organizations should immediately update to the latest versions of Visual Studio Code and the Remote - SSH extension to eliminate the risk of exploitation. In addition to patching, security teams should implement network-level restrictions to limit SSH access to trusted IP addresses and implement multi-factor authentication for remote development connections. The principle of least privilege should be enforced by limiting the permissions of remote development accounts and ensuring that environment variables are properly sanitized before being processed. Security monitoring should be enhanced to detect unusual environment variable modifications or suspicious remote access patterns. Organizations should also consider implementing network segmentation to isolate development environments from critical production systems. The vulnerability demonstrates the importance of secure coding practices and input validation, particularly in development tools that handle sensitive environment data. Security teams should conduct regular vulnerability assessments of development tools and ensure that remote development practices are properly secured. This vulnerability highlights the need for comprehensive security awareness training for developers regarding the risks associated with remote development tools and the importance of keeping development environments up to date with security patches. The ATT&CK framework categorizes this vulnerability under T1059 Command and Scripting Interpreter and T1133 External Remote Services, as it enables attackers to execute commands through legitimate development tools and access remote systems through SSH connections.