GHSA-jjc5-fp7p-6f8w
HIGHShescape prior to 1.5.8 vulnerable to insufficient escaping of line feeds for CMD
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 impacts users that use Shescape (any API function) to escape arguments for cmd.exe on Windows. An attacker can omit all arguments following their input by including a line feed character ('\n') in the payload. Example:
import cp from "node:child_process";
import * as shescape from "shescape";
// 1. Prerequisites
const options = {
shell: "cmd.exe",
};
// 2. Attack
const payload = "attacker\n";
// 3. Usage
let escapedPayload;
escapedPayload = shescape.escape(payload, options);
// Or
escapedPayload = shescape.escapeAll([payload], options)[0];
// Or
escapedPayload = shescape.quote(payload, options);
// Or
escapedPayload = shescape.quoteAll([payload], options)[0];
cp.execSync(`echo Hello ${escapedPayload}! How are you doing?`, options);
// Outputs: "Hello attacker"
Note:
execSyncis just illustrative here, all ofexec,execFile,execFileSync,fork,spawn, andspawnSynccan be attacked using a line feed character if CMD is the shell being used.
Patches
This bug has been patched in v1.5.8 which you can upgrade to now. No further changes are required.
Workarounds
Alternatively, line feed characters ('\n') can be stripped out manually or the user input can be made the last argument (this only limits the impact).
References
- https://github.com/ericcornelissen/shescape/pull/332
- https://github.com/ericcornelissen/shescape/releases/tag/v1.5.8
For more information
If you have any questions or comments about this advisory:
- Comment on https://github.com/ericcornelissen/shescape/pull/332
- 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 | 1.5.8 |
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 1.5.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-jjc5-fp7p-6f8w 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-jjc5-fp7p-6f8w 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-jjc5-fp7p-6f8w. 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-jjc5-fp7p-6f8w in your dependencies?
O3 detects GHSA-jjc5-fp7p-6f8w across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.