CVE-2026-73647: Quasar Prototype Pollution Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-3r53-75j5-3g7j",
  "modified" : "2026-08-13T17:57:16Z",
  "published" : "2026-07-24T22:36:45Z",
  "aliases" : [ "CVE-2026-73647" ],
  "summary" : "Quasar: Prototype pollution in the extend() utility",
  "details" : "### Summary\n\n`quasar@2.20.1`, the latest published version at the time of testing, appears to be vulnerable to prototype pollution through the public `extend()` utility exported from the package root.\n\nWhen `extend(true, target, source)` is used for a deep merge, attacker-controlled object keys are recursively copied into the target object without blocking prototype-pollution primitives such as `__proto__`, `constructor`, or `prototype`.\n\nThis can allow attacker-controlled properties to be written to `Object.prototype`.\n\n### Details\n\nAffected source:\n\n```text\nsrc/utils/extend/extend.js\n```\n\nDistributed files include:\n\n```text\ndist/quasar.server.prod.js\ndist/quasar.server.prod.cjs\ndist/quasar.client.js\n```\n\nThe package root publicly exports `extend`. During deep merge, source object keys are recursively assigned into the target object. If the source object contains an own `__proto__` property, the merge can descend into the prototype object and assign attacker-controlled properties onto `Object.prototype`.\n\n### PoC\n\n```bash\nrm -rf /tmp/quasar-extend-pp-poc\nmkdir /tmp/quasar-extend-pp-poc\ncd /tmp/quasar-extend-pp-poc\n\nnpm init -y >/dev/null\nnpm install quasar@2.20.1 vue@3.5.31 >/dev/null\n\ncat > hack.mjs <<'JS'\nimport { extend } from 'quasar';\n\ndelete Object.prototype.polluted;\n\nextend(true, {}, {\n  ['__proto__']: {\n    polluted: 'yes'\n  }\n});\n\nconsole.log(({}).polluted);\n\ndelete Object.prototype.polluted;\nJS\n\nnode ./hack.mjs\n```\n\nObserved output:\n\n```text\nyes\n```\n\nExpected output:\n\n```text\nundefined\n```\n\n### Impact\n\nThis is a prototype pollution vulnerability.\n\nIf an application passes user-controlled or partially user-controlled objects into `extend(true, ...)`, an attacker may be able to pollute `Object.prototype` in the same JavaScript process.\n\nDepending on how the polluted property is later consumed, this may lead to logic bypass, unsafe default option injection, denial of service, or other application-specific security impact.\n\n### Suggested Fix\n\nReject or safely ignore dangerous keys before assignment, including:\n\n```text\n__proto__\nprototype\nconstructor\n```\n\nThe merge implementation should also avoid descending into prototype-related properties during recursive merge.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "quasar"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.22.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 2.21.4"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/quasarframework/quasar/security/advisories/GHSA-3r53-75j5-3g7j"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/quasarframework/quasar/commit/d0a95d95ab3c29d13e1b8ba8c5e5025fd6ce35e7"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/quasarframework/quasar"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/quasarframework/quasar/releases/tag/quasar-v2.22.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1321" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-24T22:36:45Z",
    "nvd_published_at" : null
  }
}