n8n: Unauthenticated Persistent Storage Exhaustion via OAuth Dynamic Client Registration Endpoint
Impact
The OAuth Dynamic Client Registration endpoints validated field sizes only for redirect_uris, leaving client_name and grant_types bounded by presence checks alone. An unauthenticated remote caller could submit arbitrarily large values in either field and have them persisted to the database. Repeated registration therefore grew persistent storage without limit and without any account on the instance. The patch caps client_name at its column length and limits grant_types to the grant types the server actually implements, with the array capped at that count.
Patches
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.
Workarounds
If upgrading is not immediately possible, administrators should consider the following temporary mitigations:
- Restrict network access to the n8n instance so that only trusted clients can reach it.
- Place the instance behind a reverse proxy configured to enforce strict request body size limits below the default 16 MiB.
- Monitor database size for unexpected growth and audit the
oauth_clientstable for anomalous entries.
These workarounds do not fully remediate the risk and should only be used as short-term mitigation measures.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | n8n | >= 2.38.0, < 2.38.2, < 2.37.7 | 2.38.2, 2.37.7 |
References
- CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N- Weakness (CWE)
CWE-770- Platform
- npm
- Package
n8n- Disclosed
- 10.09.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-hh89-3r9w-qj3j - CC BY 4.0
Vulnerability history: n8n
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 156
- First → latest
- 05.2023 09.2026
- Without a fix
- 1
- Exploited in attacks
- 1
Severity breakdown
- Critical 24
- High 58
- Medium 74
Disclosures per year
- 2023: 3
- 2024: 0
- 2025: 14
- 2026: 139
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n8n: Unauthenticated Persistent Storage Exhaustion via OAuth Dynamic Client Registration Endpoint this entry
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