GHSA-66pp-5p9w-q87j
Fix: ericcornelissen/shescape#1916GHSA-66pp-5p9w-q87j is a Information Exposure vulnerability in shescape. O3 Security confirms whether GHSA-66pp-5p9w-q87j is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Shescape has potential environment variable exposure on Windows with CMD
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, a proxy for how much of the ecosystem is exposed.
shescapenpmDescription
Impact
This impact users of Shescape on Windows that explicitly configure shell: 'cmd.exe' or shell: true using any of quote/quoteAll/escape/escapeAll.
An attacker may be able to get read-only access to environment variables. Example:
import * as cp from "node:child_process";
import { Shescape } from "shescape";
// 1. Prerequisites
const shescape = new Shescape({
shell: "cmd.exe",
// Or
shell: true, // Only if the default shell is CMD
});
// 2. Payload
const payload = '"%PATH%';
// 3. Usage
let escapedPayload;
escapedPayload = shescape.quote(payload);
// Or
escapedPayload = shescape.quoteAll([payload]);
// Or
escapedPayload = shescape.escape(payload);
// Or
escapedPayload = shescape.escapeAll([payload]);
// And (example)
const result = cp.execSync(`echo Hello ${escapedPayload}`, options);
// 4. Impact
console.log(result.toString());
// Outputs "Hello" followed by the contents of the PATH environment variable
For Shescape prior to v2.0.0, the options object must have shell: 'cmd.exe' or shell: undefined and interpolation: true.
Patches
This bug has been patched in v2.1.2 which you can upgrade to now.
If you are already using v2 of Shescape, no further changes are required. If you are using v1 of Shescape, follow the migration guide to upgrade to v2. There is no plan to release a patch compatible with v1 of Shescape.
Workarounds
Alternatively, users can remove all instances of % from user input before using Shescape.
References
For more information
- Comment on Pull Request #1916
- Comment on commit 0a81f1e
- Open an issue at https://github.com/ericcornelissen/shescape/issues (New issue > Question)
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | shescape | ≥ 1.7.2&&< 2.1.2 | 2.1.2 |
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 2.1.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-66pp-5p9w-q87j 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-66pp-5p9w-q87j 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-66pp-5p9w-q87j. 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-66pp-5p9w-q87j in your dependencies?
O3 detects GHSA-66pp-5p9w-q87j across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.