CVE-2026-42236— n8n: Unauthenticated Denial of Service via MCP Client Registration
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I. Basic Information for CVE-2026-42236
Vulnerability Information
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Vulnerability Title
n8n: Unauthenticated Denial of Service via MCP Client Registration
Source: NVD (National Vulnerability Database)
Vulnerability Description
n8n is an open source workflow automation platform. Prior to versions 1.123.32, 2.17.4, and 2.18.1, the MCP OAuth client registration endpoint accepted unauthenticated requests and stored client data without adequate resource controls. An unauthenticated remote attacker could exhaust server memory resources by sending large registration payloads, rendering the n8n instance unavailable. The MCP enable/disable toggle gates MCP access but did not restrict client registrations, meaning the endpoint is reachable regardless of whether MCP access is enabled on the instance. This issue has been patched in versions 1.123.32, 2.17.4, and 2.18.1.
Source: NVD (National Vulnerability Database)
CVSS Information
N/A
Source: NVD (National Vulnerability Database)
Vulnerability Type
不加限制或调节的资源分配
Source: NVD (National Vulnerability Database)
Vulnerability Title
n8n 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
n8n是n8n开源的一个可扩展的工作流自动化工具。 n8n 1.123.32之前版本、2.17.4之前版本和2.18.1之前版本存在安全漏洞，该漏洞源于MCP OAuth客户端注册端点接受未经身份验证的请求且未对客户端数据进行充分资源控制，可能导致未经身份验证的远程攻击者通过发送大型注册有效载荷耗尽服务器内存资源，导致n8n实例不可用。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
II. Public POCs for CVE-2026-42236
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Same Patch Batch · n8n-io · 2026-05-04 · 12 CVEs total
| CVE-2026-42232 | n8n: XML Node Prototype Pollution to RCE | |
| CVE-2026-42233 | n8n: SQL Injection in Oracle Database Node via Limit Field | |
| CVE-2026-42229 | n8n: SQL Injection in SeaTable Node | |
| CVE-2026-42228 | n8n: Hijacking of Unauthenticated Chat Execution | |
| CVE-2026-42235 | n8n: XSS via MCP OAuth client | |
| CVE-2026-42237 | n8n: SQL Injection in Snowflake and MySQL Nodes | |
| CVE-2026-42226 | n8n: Credential Authorization Bypass in dynamic-node-parameters Allows Foreign API Key Rep | |
| CVE-2026-42230 | n8n: Open Redirect in MCP OAuth Consent Flow | |
| CVE-2026-42234 | n8n: Python Task Runner Sandbox Escape | |
| CVE-2026-42227 | n8n: Public API Variables IDOR Allows Cross-Project Secret Disclosure | |
| CVE-2026-42231 | n8n: Prototype Pollution in XML Webhook Body Parser Leads to RCE |
IV. Related Vulnerabilities
Same vendor: n8n-io
Same weakness: CWE-770
- CVE-2026-42294
Argo Workflows: Unauthenticated Memory Exhaustion (DoS) in W - CVE-2026-42189
Russh: Pre-auth DoS via unbounded allocation in keyboard-int - CVE-2026-42793
Atom table exhaustion via attacker-controlled GraphQL SDL na - CVE-2026-44499
ZEBRA: Permanent Block Discovery Halt via Gossip Queue Satur - CVE-2026-44500
ZEBRA: Allocation Amplification in Inbound Network Deseriali
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