CVE-2026-59206: n8n Prototype Pollution Allows Unauthenticated Access to Sensitive Endpoints

Technical summary

The vulnerability is a prototype pollution flaw (CWE-1321) in n8n versions prior to 1.123.61, 2.27.4, and 2.28.1. An authenticated user with workflow:create permission can craft a workflow that, when saved, updated, or imported via the workflow API, pollutes Object.prototype in the Node.js runtime. This manipulation allows the platform's permission checks to fail in a way that grants unauthenticated requests the same access level as authenticated ones. The attack surface is the workflow API itself, making this exploitable without requiring privileged user credentials—only the ability to create workflows, which is a default permission in many deployments.

Business impact

This vulnerability degrades the security boundary between authenticated and unauthenticated access. An attacker who gains workflow creation rights (through a legitimate account, weak credentials, or social engineering) can expose the user and project directory to anyone on the network, enabling account enumeration, targeting, and social engineering attacks. In multi-tenant or shared n8n deployments, this could allow visibility into workflows and projects across organizational boundaries. The high CVSS score (7.1) reflects the combination of network accessibility, low attack complexity, and significant confidentiality impact, though the requirement for initial authentication limits widespread abuse to those with some level of platform access.

Affected systems

All n8n deployments running versions prior to 1.123.61 (in the 1.x branch), 2.27.4 (in the 2.x branch up to 2.27), or 2.28.1 (in the 2.x branch at 2.28) are affected. This includes self-hosted instances and cloud deployments. Organizations using n8n for critical workflow automation, API integrations, or multi-user collaboration environments face the greatest risk due to larger user bases and higher-value targets within the user directory.

Exploitability

Exploitation requires an authenticated n8n account with the default workflow:create permission—a very common baseline permission in standard deployments. No specialized tools, zero-day exploits, or user interaction is required once the malicious workflow is created. The attack is repeatable, can be executed from any network location with access to the n8n API, and leaves minimal forensic traces if logging is not configured to capture workflow API payloads in detail. The lack of KEV (Known Exploited Vulnerability) status does not imply exploitation is difficult; rather, it indicates no exploitation in the wild has been reported to CISA at this time. Given the straightforward nature of prototype pollution and the accessibility of the attack vector, practical weaponization is feasible for skilled attackers.

Remediation

Upgrade n8n immediately to version 1.123.61, 2.27.4, or 2.28.1 depending on your branch. These releases patch the prototype pollution flaw by implementing proper input validation and object property handling in the workflow API. No workarounds are available; patching is the only remediation. For organizations unable to patch immediately, restrict workflow:create permissions to trusted users only, and monitor workflow API calls for suspicious payloads.

Patch guidance

Identify your current n8n version (visible in the admin panel or via API). If running 1.x, upgrade to at least 1.123.61. If running 2.x below 2.27, upgrade to 2.27.4. If running 2.28.0, upgrade to 2.28.1. Test patches in a staging environment that mirrors production authentication and multi-user scenarios before rolling out to production. Backup your n8n database and credentials before upgrading. Verify after upgrade that workflow creation, API calls, and permission checks function as expected.

Detection guidance

Monitor n8n workflow API logs for POST/PUT requests to /workflows endpoints that contain unusual object notation or property names, particularly those with __proto__, constructor, or prototype in the payload. Alert on any workflow creation or update by users who do not typically create workflows. Check for unauthenticated requests to /users or /projects endpoints succeeding without proper authentication headers. If SIEM integration is available, correlate workflow API activity with unexpected API calls to sensitive endpoints. Review audit logs for workflows created with suspicious or obfuscated names that might indicate an attack attempt.

Why prioritize this

This vulnerability merits immediate attention for any organization running n8n, particularly in production or multi-tenant environments. The combination of ease of exploitation (default permissions, simple API call), significant impact (confidentiality breach, directory traversal), and the sensitivity of user and project metadata in automation platforms warrants rapid patching. The fact that it requires only low-privilege authentication means breach likelihood is higher than vulnerabilities requiring administrative access.

Risk score, explained

The CVSS 7.1 (HIGH) score reflects: network accessibility without additional complexity (AV:N/AC:L), a requirement for prior authentication (PR:L) that is met by default permissions rather than admin roles, no user interaction required (UI:N), confidentiality impact from exposed endpoints (C:H), and moderate availability impact from potential resource exhaustion or performance degradation (A:L). The score does not account for organizational context, such as whether the n8n instance is internet-exposed or restricted to internal networks, or the sensitivity of user and project data stored within.

Frequently asked questions