CVE-2026-27496: n8n Information Disclosure Vulnerability

CVE-2026-27496 Overview

CVE-2026-27496 is an Uninitialized Memory Use vulnerability in n8n, an open source workflow automation platform. This vulnerability allows authenticated users with workflow creation or modification permissions to exploit the JavaScript Task Runner to allocate uninitialized memory buffers. These buffers may contain residual data from the same Node.js process, potentially exposing sensitive information including data from prior requests, tasks, secrets, or authentication tokens.

Critical Impact

Authenticated attackers can exploit uninitialized memory buffers to disclose sensitive in-process data including secrets, tokens, and data from prior requests processed by the same Node.js process.

Affected Products

• n8n versions prior to 1.123.22
• n8n versions prior to 2.9.3
• n8n versions prior to 2.10.1

Discovery Timeline

• 2026-03-25 - CVE CVE-2026-27496 published to NVD
• 2026-03-26 - Last updated in NVD database

Technical Details for CVE-2026-27496

Vulnerability Analysis

This vulnerability is classified under CWE-908 (Use of Uninitialized Resource). The flaw exists within n8n's JavaScript Task Runner component, which can be exploited when Task Runners are enabled using the N8N_RUNNERS_ENABLED=true configuration flag.

When an authenticated user with appropriate permissions creates or modifies a workflow, they can craft malicious workflow logic that triggers the allocation of uninitialized memory buffers within the Task Runner. Since these buffers are not properly initialized before use, they may contain residual data from prior operations within the same Node.js process. This residual data can include highly sensitive information such as API tokens, authentication secrets, workflow data from other users, or internal system information.

The vulnerability requires network access and low-privilege authentication to exploit. No user interaction is required for successful exploitation. When running in external runner mode (N8N_RUNNERS_MODE=external), the impact is limited to data within the isolated external runner process, providing partial containment of the information exposure.

Root Cause

The root cause of CVE-2026-27496 lies in improper memory handling within n8n's JavaScript Task Runner. When allocating memory buffers for task execution, the application fails to properly initialize the memory contents before use. In Node.js environments, uninitialized Buffer objects may contain data from previously allocated and freed memory regions. This allows an attacker to read memory contents that should have been cleared, enabling unauthorized access to sensitive data that was processed earlier in the same process lifecycle.

Attack Vector

The attack vector for this vulnerability requires network access with authenticated user permissions. An attacker must have legitimate credentials with workflow creation or modification privileges on the n8n platform. The attack flow involves:

1. The attacker authenticates to the n8n platform with a user account that has workflow creation or editing permissions
2. The attacker creates or modifies a workflow to include JavaScript code that triggers uninitialized buffer allocation
3. When the Task Runner executes the malicious workflow, it allocates buffers without proper initialization
4. The attacker reads the buffer contents to extract residual sensitive data from the Node.js process memory

The vulnerability mechanism involves improper buffer allocation in the JavaScript Task Runner. When buffers are allocated without explicit initialization, they may retain data from previous memory operations. For detailed technical information, refer to the GitHub Security Advisory GHSA-xvh5-5qg4-x9qp.

Detection Methods for CVE-2026-27496

Indicators of Compromise

• Unusual workflow creation or modification activity from users, particularly workflows with custom JavaScript code targeting buffer operations
• Unexpected memory allocation patterns or errors in Task Runner logs
• Workflows containing code that explicitly allocates buffers without initialization (e.g., Buffer.allocUnsafe())
• Anomalous data access patterns where users retrieve information outside their normal workflow scope

Detection Strategies

• Monitor n8n workflow creation and modification events for suspicious JavaScript code patterns
• Implement logging for Task Runner execution and analyze for unusual buffer allocation activity
• Review user activity logs for accounts with workflow permissions that show atypical behavior patterns
• Deploy application-level monitoring to detect attempts to read uninitialized memory contents

Monitoring Recommendations

• Enable detailed logging for the JavaScript Task Runner component
• Configure alerting for workflow modifications by non-administrative users
• Monitor for unusual outbound data transfers that may indicate successful data exfiltration
• Implement periodic auditing of workflows containing custom JavaScript code

How to Mitigate CVE-2026-27496

Immediate Actions Required

• Upgrade n8n to version 1.123.22, 2.9.3, or 2.10.1 or later immediately
• Audit existing workflows for any suspicious JavaScript code that may exploit buffer allocation
• Review and restrict workflow creation and editing permissions to fully trusted users only
• If Task Runners are not required, consider disabling them by removing the N8N_RUNNERS_ENABLED=true configuration

Patch Information

The n8n development team has released security patches addressing this vulnerability in versions 1.123.22, 2.9.3, and 2.10.1. Users should upgrade to these versions or later to fully remediate the vulnerability. Detailed patch information and upgrade instructions can be found in the GitHub Security Advisory and the n8n Configuration Guide.

Workarounds

• Limit workflow creation and editing permissions to fully trusted users only until patching is possible
• Enable external runner mode by setting N8N_RUNNERS_MODE=external to isolate the runner process and limit data exposure
• Review and block potentially dangerous nodes using n8n's security blocking nodes feature
• These workarounds do not fully remediate the risk and should only be used as short-term mitigation measures

# Configuration example for enabling external runner mode
# Add to your n8n environment configuration
N8N_RUNNERS_MODE=external