Locutus Prototype Pollution due to incomplete fix for CVE-2026-25521

{
  "id": "8bf658af7cbf8f37cd2513b8636f4426a1b10561ec502cc3927a12a2da796b08",
  "url": "https://osv.dev/vulnerability/CVE-2026-33994",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Locutus Prototype Pollution due to incomplete fix for CVE-2026-25521",
    "summary": "Locutus brings stdlibs of other programming languages to JavaScript for educational purposes. Starting in version 2.0.39 and prior to version 3.0.25, a prototype pollution vulnerability exists in the `parse_str` function of the npm package locutus. An attacker can pollute `Object.prototype` by overriding `RegExp.prototype.test` and then passing a crafted query string to `parse_str`, bypassing the prototype pollution guard. This vulnerability stems from an incomplete fix for CVE-2026-25521. The CVE-2026-25521 patch replaced the `String.prototype.includes()`-based guard with a `RegExp.prototype.test()`-based guard. However, `RegExp.prototype.test` is itself a writable prototype method that can be overridden, making the new guard bypassable in the same way as the original — trading one hijackable built-in for another. Version 3.0.25 contains an updated fix.",
    "evidence": "osv:CVE-2026-33994",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-33994",
      "aliases": [
        "CVE-2026-33994",
        "GHSA-vc8f-x9pp-wf5p"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/locutusjs/locutus",
              "type": "GIT",
              "events": [
                {
                  "introduced": "fb90ed0cb832897ef15880be446ab124e3313047"
                },
                {
                  "fixed": "0d2402bdb92f9c59918114af9c8ba628f22e9152"
                },
                {
                  "fixed": "345a6211e1e6f939f96a7090bfeff642c9fcf9e4"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:locutus:locutus:*:*:*:*:*:node.js:*:*",
                    "range": [
                      {
                        "introduced": "2.0.39"
                      },
                      {
                        "fixed": "3.0.25"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "345a6211e1e6f939f96a7090bfeff642c9fcf9e4"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "0d2402bdb92f9c59918114af9c8ba628f22e9152"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "v3.0.25"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v3.0.24",
            "v3.0.23",
            "v3.0.22",
            "v3.0.21",
            "v3.0.20",
            "v3.0.19",
            "v3.0.18",
            "v3.0.17",
            "v3.0.16",
            "v3.0.15",
            "v3.0.14",
            "v3.0.13",
            "v3.0.12",
            "v3.0.11",
            "v3.0.10",
            "v3.0.9",
            "v3.0.8",
            "v3.0.7",
            "v3.0.6",
            "v3.0.5",
            "v3.0.4",
            "v3.0.3",
            "v3.0.2",
            "v3.0.1",
            "v3.0.0",
            "v2.0.39"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-33994.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:22.519776959Z",
      "provider": "osv",
      "references": [
        "https://github.com/locutusjs/locutus/releases/tag/v3.0.25",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33994.json",
        "https://github.com/locutusjs/locutus/security/advisories/GHSA-vc8f-x9pp-wf5p",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-33994",
        "https://github.com/locutusjs/locutus/commit/345a6211e1e6f939f96a7090bfeff642c9fcf9e4",
        "https://github.com/locutusjs/locutus/pull/597"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-1321"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33994.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-33994",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 488510,
  "published_at": "2026-03-27T22:15:47.131+00:00"
}