---
id: CVE-2026-39911
title: Hashgraph Guardian 3.5.1 Unsandboxed JavaScript Execution RCE
summary: >-
  Hashgraph Guardian through version 3.5.1, fixed in commit 45fbe2f, contains an
  unsandboxed JavaScript execution vulnerability in the Custom Logic policy
  block worker that allows authenticated Standard Registry users to execute
  arbitrary …
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
cwe:
  - CWE-668
vendor: hashgraph
product: guardian
affected:
  - guardian <= 3.5.1
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-04-09T18:15:34.979616Z'
published: '2026-04-09'
updated: '2026-11-08'
sourceUpdated: '2026-11-08T14:02:32.250Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-39911'
references:
  - url: 'https://github.com/hashgraph/guardian/pull/5929'
  - url: >-
      https://github.com/hashgraph/guardian/commit/45fbe2f7e0e8feee30105d42d66ed63fb6177ebe
  - url: >-
      https://www.vulncheck.com/advisories/hashgraph-guardian-unsandboxed-javascript-execution-rce
tags:
  - cve.org
epss: 0.00554
epssPercentile: 0.4653
ingestedAt: '2026-11-08T14:51:22.449Z'
---

## Overview

Hashgraph Guardian through version 3.5.1, fixed in commit 45fbe2f, contains an unsandboxed JavaScript execution vulnerability in the Custom Logic policy block worker that allows authenticated Standard Registry users to execute arbitrary code by passing user-supplied JavaScript expressions directly to the Node.js Function() constructor without isolation. Attackers can import native Node.js modules to read arbitrary files from the container filesystem, access process environment variables containing sensitive credentials such as RSA private keys, JWT signing keys, and API tokens, and forge valid authentication tokens for any user including administrators.

## Affected

- `guardian <= 3.5.1`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.