GHSA-j55r-787p-m549
HIGHShescape on Windows escaping may be bypassed in threaded context
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
shescapenpmDescription
Impact
This may impact users that use Shescape on Windows in a threaded context (e.g. using Worker threads). The vulnerability can result in Shescape escaping (or quoting) for the wrong shell, thus allowing attackers to bypass protections depending on the combination of expected and used shell.
This snippet demonstrates a vulnerable use of Shescape:
// 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);
}
});
}
Patches
This bug has been patched in v1.7.4 which you can upgrade to now. No further changes are required.
Workarounds
If you are impacted there is no workaround possible.
References
For more information
- Comment on Pull Request #1142
- Comment on commit
0b976da - Open an issue at https://github.com/ericcornelissen/shescape/issues (New issue > Question > Get started)
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | shescape | all versions | 1.7.4 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for shescape. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update shescape to 1.7.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-j55r-787p-m549 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-j55r-787p-m549 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-j55r-787p-m549. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-j55r-787p-m549 in your dependencies?
O3 detects GHSA-j55r-787p-m549 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.