CVE-2026-72769 Overview
CVE-2026-72769 is a prototype pollution vulnerability in n8n, the open-source workflow automation platform. The flaw resides in the VM expression engine and affects versions prior to 1.123.67, 2.31.5, and 2.32.1. An authenticated user with permission to create or edit workflow expressions can abuse array-element access to obtain a reference to a host built-in object. The attacker then pollutes its prototype inside the main n8n process, escaping the sandbox and causing a denial of service. Both self-hosted and cloud instances running the VM expression engine are affected [CWE-1321].
Critical Impact
Authenticated workflow editors can escape the expression sandbox and crash the main n8n process, disrupting all automated workflows on the instance.
Affected Products
- n8n self-hosted versions prior to 1.123.67
- n8n versions prior to 2.31.5
- n8n versions prior to 2.32.1 (including n8n Cloud instances running the VM expression engine)
Discovery Timeline
- 2026-08-11 - CVE-2026-72769 published to the National Vulnerability Database
- 2026-08-11 - Last updated in NVD database
Technical Details for CVE-2026-72769
Vulnerability Analysis
n8n allows users to embed JavaScript expressions inside workflow nodes. These expressions execute in a VM-based sandbox that is intended to isolate user input from the host n8n process. The vulnerable expression engine does not sufficiently restrict access to host built-in objects when array-element access syntax is used. An authenticated user constructs a workflow expression that returns a reference to a host built-in, then modifies its prototype. The modification persists inside the main n8n process rather than staying inside the sandbox. Because the polluted prototype is shared with core JavaScript objects, subsequent operations in the main process encounter unexpected properties and fail, producing a denial of service.
Root Cause
The root cause is improper control of modification of object prototype attributes [CWE-1321] within the VM expression engine. Array-element access is not proxied or wrapped in a way that prevents user-controlled expressions from reaching host-side constructor prototypes. This gap collapses the boundary between the sandboxed expression context and the parent n8n Node.js process.
Attack Vector
Exploitation requires an authenticated account with permission to create or edit workflow expressions. The attacker submits a malicious expression that references and mutates a host built-in prototype. When the workflow executes, the prototype change propagates to the main n8n process and destabilizes it. No user interaction beyond normal workflow execution is required. See the GitHub Security Advisory GHSA-hx4h-vr3m-45vh and the VulnCheck Advisory for n8n for further technical detail.
Detection Methods for CVE-2026-72769
Indicators of Compromise
- Unexpected crashes or restarts of the main n8n process shortly after workflow execution or edit events.
- Workflow expressions containing suspicious array-index access patterns such as constructor, __proto__, or prototype references.
- Audit log entries showing workflow creation or modification by low-privilege accounts immediately preceding service failure.
Detection Strategies
- Review the n8n workflow database for expression fields containing __proto__, constructor.prototype, or similar prototype-chain lookups.
- Correlate workflow edit or execution events with Node.js process termination events in host logs.
- Alert on repeated n8n service restarts across a short time window, which may indicate exploitation attempts.
Monitoring Recommendations
- Enable n8n audit logging for workflow create, update, and execute actions and forward the events to a central log store.
- Monitor the n8n container or systemd unit for abnormal exit codes and restart loops.
- Track authenticated user activity for accounts that create workflows containing complex JavaScript expressions.
How to Mitigate CVE-2026-72769
Immediate Actions Required
- Upgrade self-hosted n8n to version 1.123.67, 2.31.5, 2.32.1, or later immediately.
- Restrict workflow creation and edit permissions to trusted users until the patch is applied.
- Review recently created or modified workflows for suspicious expression content.
- Rotate credentials stored in n8n if unauthorized workflow modifications are found.
Patch Information
n8n has released fixed versions 1.123.67, 2.31.5, and 2.32.1 that address the prototype pollution issue in the VM expression engine. Cloud instances are updated by the vendor. Self-hosted operators must upgrade manually. Refer to the GitHub Security Advisory GHSA-hx4h-vr3m-45vh for release details.
Workarounds
- Limit workflow editor role assignments to a minimal set of administrators until patched.
- Place the n8n instance behind an authenticated reverse proxy and disable public registration.
- Configure the process manager to auto-restart n8n on failure to reduce downtime while patching is scheduled.
# Upgrade n8n via npm to a patched release
npm install -g n8n@1.123.67
# Or pull the fixed Docker image and restart the container
docker pull n8nio/n8n:1.123.67
docker stop n8n && docker rm n8n
docker run -d --name n8n -p 5678:5678 n8nio/n8n:1.123.67
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
