CVE-2020-8178

Vulnerability

Overview

The npm package jison (a JavaScript parser generator) in versions up to and including 0.4.18 is vulnerable to OS command injection due to insufficient input validation [1]. The flaw exists when the library processes user-supplied grammar definitions or other inputs that are passed unsanitized to shell commands during the generation of parser code.

Attack

Vector and Prerequisites

An attacker could exploit this vulnerability by crafting a malicious input (e.g., a .jison grammar file) that contains shell metacharacters. When jison handles the input, the unsanitized content is interpolated into a system command, allowing arbitrary command execution. No special network position is required if the attacker can supply the input directly, though the threat surface primarily affects applications or build pipelines that accept external grammar files without validation.

Impact

Successful exploitation permits arbitrary OS command execution with the privileges of the process running jison. This can lead to full server compromise, data exfiltration, installation of malware, or lateral movement within the environment, depending on the deployment context.

Mitigation

The vulnerability has been addressed in versions after 0.4.18. Users should upgrade to the latest patched release immediately. For applications that embed jison in build or runtime tooling, input validation and sanitization of grammar files should be enforced as a defense-in-depth measure. The issue was reported through HackerOne and is publicly documented [1].