AI Sec Watch: A Security Intelligence Platform for AI Systems

Luu, T.J.

GHSA-679f-58pq-4v2c: n8n: Prototype Pollution via Workflow Structure Summary Can Lead to Denial of Service

mediumvulnerability

security

Source: GitHub Advisory DatabaseSeptember 10, 2026CVE-2026-86078

Summary

n8n has a prototype pollution vulnerability (a bug where attackers can modify the base object that all objects inherit from) in its AI workflow summary feature. An attacker can bypass the client-side name restrictions by sending specially crafted requests directly to the API, using reserved names like `__proto__` to corrupt the shared object prototype and cause denial of service (making the service unavailable) for all users. The vulnerability affects how the workflow summary builds its results by using arbitrary strings from the workflow without proper validation.

Solution / Mitigation

The issue has been fixed in n8n versions 2.37.7 and 2.38.2. Users should upgrade to one of these versions or later to remediate the vulnerability. If upgrading is not immediately possible, temporary workarounds include: restricting n8n instance access to fully trusted users only, removing or leaving unconfigured the `N8N_INSTANCE_AI_MODEL*` environment variables to prevent the Instance AI module from reaching the vulnerable code path, and restarting the n8n process to clear any in-memory prototype pollution if an attack is suspected. Note that these workarounds do not fully remediate the risk and should only be used as short-term mitigation measures.