Improper Neutralization Affecting shescape package, versions <1.7.4
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-JS-SHESCAPE-5849592
- published23 Aug 2023
- disclosed22 Aug 2023
- creditUnknown
Introduced: 22 Aug 2023
CVE-2023-40185 (opens in a new tab)How to fix?
Upgrade shescape to version 1.7.4 or higher.
Overview
shescape is a simple shell escape library
Affected versions of this package are vulnerable to Improper Neutralization due to possible escaping the wrong shell, thus allowing attackers to bypass protections. Note: you are only vulnerable if you are using this package on Windows in a threaded context.
PoC
// vulnerable.js
import { exec } from "node:child_process";
import { Worker, isMainThread } from 'node:worker_threads';
import * as shescape from "shescape";
if (isMainThread) {
// 1. Something like a worker thread must be used. The reason being that they
// unexpectedly change environment variable names on Windows.
new Worker("./vulnerable.js");
} else {
// 2. Example configuration that's problematic. In this setup example the
// expected default system shell is CMD. We configure the use of PowerShell.
// Shescape will fail to look up PowerShell and default to escaping for CMD
// instead, resulting in the vulnerability.
const options = {
shell: "powershell",
interpolation: true,
};
// 3. Using shescape to protect against attacks, this is correct.
const escaped = shescape.escape("&& ls", options);
// 4. Invoking a command with the escaped user input, this is vulnerable in
// this case.
exec(`echo Hello ${escaped}`, options, (error, stdout) => {
if (error) {
console.error(`An error occurred: ${error}`);
} else {
console.log(stdout);
}
});
}