CVE-2019-10769 in safer-eval
Summary
by MITRE
safer-eval is a npm package to sandbox the he evaluation of code used within the eval function. Affected versions of this package are vulnerable to Arbitrary Code Execution via generating a RangeError.
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Analysis
by VulDB Data Team • 03/07/2024
The safer-eval npm package represents a critical security vulnerability classified as CVE-2019-10769, where the package's attempt to create a secure sandbox environment for code evaluation inadvertently introduces a path for arbitrary code execution. This package was designed to provide a safer alternative to the standard eval function by implementing sandboxing mechanisms to prevent malicious code from accessing sensitive system resources. However, the implementation contains a fundamental flaw that allows attackers to bypass these security measures through a specific exploitation technique involving RangeError generation. The vulnerability stems from the package's insufficient handling of error conditions during code evaluation, creating a scenario where crafted malicious input can trigger a RangeError that ultimately leads to code execution outside the intended sandbox boundaries. This represents a classic case of inadequate input validation and error handling that undermines the core security premise of the library.
The technical flaw manifests when the safer-eval package processes certain malformed inputs that cause it to generate a RangeError exception. Rather than properly handling this error condition and maintaining the sandbox integrity, the package's implementation allows the RangeError to propagate in a way that enables attackers to inject and execute arbitrary code. The vulnerability specifically exploits the interaction between the package's internal error handling mechanisms and JavaScript's execution environment, creating an unexpected code path that bypasses the sandbox protections. This flaw falls under the CWE-787 Out-of-bounds Write category, as the package's error handling creates conditions where memory boundaries are violated, and it aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter: JavaScript, demonstrating how the vulnerability can be leveraged to execute malicious JavaScript code. The exploitation requires minimal input crafting and can be automated, making it particularly dangerous for applications that rely on this package for code evaluation.
The operational impact of CVE-2019-10769 extends beyond immediate code execution capabilities, as it fundamentally compromises the security model that developers expect from sandboxing libraries. Applications using affected versions of safer-eval become vulnerable to remote code execution attacks, potentially allowing attackers to gain full control over affected systems, access sensitive data, or use the compromised systems as launch points for further attacks. The vulnerability affects any system that depends on this package for evaluating untrusted code, including web applications, server-side processing systems, and any environment where dynamic code execution is required but security is paramount. Organizations using this package may experience severe consequences including data breaches, system compromise, and regulatory violations, as the vulnerability essentially nullifies the security assurances that the library was designed to provide. The attack surface is particularly broad since the package was widely used across various Node.js applications and could be exploited through multiple vectors including user input processing, configuration file evaluation, and dynamic code generation scenarios.
Mitigation strategies for CVE-2019-10769 require immediate action to address the vulnerability in affected systems. The primary recommendation is to upgrade to a patched version of the safer-eval package or replace it entirely with more secure alternatives such as vm2, which provides better sandboxing capabilities and has been designed to prevent exactly these types of exploitation scenarios. Organizations should conduct comprehensive vulnerability assessments to identify all applications and systems using affected versions of the package, and implement proper input validation and sanitization measures to prevent exploitation attempts. Additionally, security teams should monitor for any signs of exploitation attempts and ensure that all development environments have updated dependencies. The remediation process must include thorough testing to ensure that the replacement solutions maintain the required functionality while providing enhanced security guarantees. Organizations should also consider implementing runtime protection measures such as intrusion detection systems and application whitelisting to prevent unauthorized code execution, and they should review their dependency management processes to ensure that vulnerable packages are identified and addressed promptly. The vulnerability underscores the importance of rigorous security testing for sandboxing libraries and demonstrates how seemingly innocuous error handling can create critical security weaknesses in security-critical components.