CVE-2026-34156: NocoBase Affected by Sandbox Escape to RCE via console._stdout Prototype Chain Traversal in Workflow Script Node

Should you act?

Critical, preconditions apply

Severe if exploited, but exploitation needs conditions that may not apply to you. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 6.8%, percentile 94: FIRST’s model estimates a 6.8% chance of exploitation activity in the next 30 days, higher than 94% of all scored CVEs (elevated). EPSS is a probability, not a verdict.
• Needs an account (low (any account)). Exposure depends on who can log in.
• Only applies if your dependency tree includes @nocobase/plugin-workflow-javascript (npm) <= 2.0.27, fixed in 2.0.28. Check your lockfile, including transitive dependencies.

What it is

NocoBase is an AI-powered no-code/low-code platform for building business applications and enterprise solutions. Prior to version 2.0.28, NocoBase's Workflow Script Node executes user-supplied JavaScript inside a Node.js vm sandbox with a custom require allowlist (controlled by WORKFLOWSCRIPTMODULES env var). However, the console object passed into the sandbox context exposes host-realm WritableWorkerStdio stream objects via console.stdout and console.stderr. An authenticated attacker can traverse the prototype chain to escape the sandbox and achieve Remote Code Execution as root. This issue has been patched in version 2.0.28.

From the GitHub advisory

## Summary

NocoBase's Workflow Script Node executes user-supplied JavaScript inside a Node.js vm sandbox with a custom require allowlist (controlled by WORKFLOWSCRIPTMODULES env var). However, the console object passed into the sandbox context exposes host-realm WritableWorkerStdio stream objects via console.stdout and console.stderr.

An authenticated attacker can traverse the prototype chain to escape the sandbox and achieve Remote Code Execution (RCE) as root.

Exploit Chain

1. console.stdout.constructor.constructor → host-realm Function constructor 2. Function('return process')() → Node.js process object 3. process.mainModule.require('childprocess') → unrestricted module loading 4. childprocess.execSync('id') → RCE as root

Weakness type: CWE-913.

Product: @nocobase/plugin-workflow-javascript (npm) · Assigned by: GitHub_M · Published: 2026-03-31

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: low (any account)
• User interaction: none
• Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation poc, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 6.79% probability of exploitation activity in the next 30 days; percentile 94.

Timeline

• 2026-03-30 — GitHub-reviewed advisory GHSA-px3p-vgh9-m57c published (critical)
• 2026-03-31 — CVE record published by GitHub_M
• 2026-04-02 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-px3p-vgh9-m57c github.com
2. CVE.org record CVE-2026-34156 cve.org
3. NVD entry CVE-2026-34156 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com

Critical npm advisories · Today’s Security Digest