GHSA-j55r-787p-m549 is a high-severity (CVSS 8.6) CWE-150 vulnerability in shescape. 1 public exploit reference exists, so weaponization risk is real. A fix is available for shescape — see the affected versions and patch details below.
Shescape on Windows escaping may be bypassed in threaded context
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-j55r-787p-m549.
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.
How urgent is this, really
GHSA-j55r-787p-m549 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 379,145 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
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 | 1.7.4npm install shescape@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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-j55r-787p-m549 can be triaged on real exposure rather than presence alone.
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 Security finds GHSA-j55r-787p-m549 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.