CVE-2026-42236 (GCVE-0-2026-42236)
Vulnerability from cvelistv5 – Published: 2026-05-04 18:38 – Updated: 2026-05-04 19:59
VLAI
EPSS
VEX
Title
n8n: Unauthenticated Denial of Service via MCP Client Registration
Summary
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.
Severity
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-05-04 19:59 UTC
CWE
- CWE-770 - Allocation of Resources Without Limits or Throttling
Assigner
GitHub_M
CNA
References
1 reference
| URL | Tags |
|---|---|
| https://github.com/n8n-io/n8n/security/advisories… | x_refsource_CONFIRM |
Impacted products
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-42236",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "yes"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-05-04T19:59:10.326960Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-05-04T19:59:24.621Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"product": "n8n",
"vendor": "n8n-io",
"versions": [
{
"status": "affected",
"version": "\u003c 1.123.32"
},
{
"status": "affected",
"version": "\u003e= 2.17.0, \u003c 2.17.4"
},
{
"status": "affected",
"version": "\u003e= 2.18.0, \u003c 2.18.1"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "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."
}
],
"metrics": [
{
"cvssV4_0": {
"attackComplexity": "LOW",
"attackRequirements": "NONE",
"attackVector": "NETWORK",
"baseScore": 8.7,
"baseSeverity": "HIGH",
"privilegesRequired": "NONE",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"vectorString": "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",
"version": "4.0",
"vulnAvailabilityImpact": "HIGH",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "NONE"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-770",
"description": "CWE-770: Allocation of Resources Without Limits or Throttling",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-05-04T18:38:51.626Z",
"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"shortName": "GitHub_M"
},
"references": [
{
"name": "https://github.com/n8n-io/n8n/security/advisories/GHSA-49m9-pgww-9vq6",
"tags": [
"x_refsource_CONFIRM"
],
"url": "https://github.com/n8n-io/n8n/security/advisories/GHSA-49m9-pgww-9vq6"
}
],
"source": {
"advisory": "GHSA-49m9-pgww-9vq6",
"discovery": "UNKNOWN"
},
"title": "n8n: Unauthenticated Denial of Service via MCP Client Registration"
}
},
"cveMetadata": {
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"cveId": "CVE-2026-42236",
"datePublished": "2026-05-04T18:38:51.626Z",
"dateReserved": "2026-04-25T05:37:12.117Z",
"dateUpdated": "2026-05-04T19:59:24.621Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-42236",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "yes"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-05-04T19:59:10.326960Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-05-04T19:59:13.387Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"product": "n8n",
"vendor": "n8n-io",
"versions": [
{
"status": "affected",
"version": "\u003c 1.123.32"
},
{
"status": "affected",
"version": "\u003e= 2.17.0, \u003c 2.17.4"
},
{
"status": "affected",
"version": "\u003e= 2.18.0, \u003c 2.18.1"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "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."
}
],
"metrics": [
{
"cvssV4_0": {
"attackComplexity": "LOW",
"attackRequirements": "NONE",
"attackVector": "NETWORK",
"baseScore": 8.7,
"baseSeverity": "HIGH",
"privilegesRequired": "NONE",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"vectorString": "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",
"version": "4.0",
"vulnAvailabilityImpact": "HIGH",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "NONE"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-770",
"description": "CWE-770: Allocation of Resources Without Limits or Throttling",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-05-04T18:38:51.626Z",
"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"shortName": "GitHub_M"
},
"references": [
{
"name": "https://github.com/n8n-io/n8n/security/advisories/GHSA-49m9-pgww-9vq6",
"tags": [
"x_refsource_CONFIRM"
],
"url": "https://github.com/n8n-io/n8n/security/advisories/GHSA-49m9-pgww-9vq6"
}
],
"source": {
"advisory": "GHSA-49m9-pgww-9vq6",
"discovery": "UNKNOWN"
},
"title": "n8n: Unauthenticated Denial of Service via MCP Client Registration"
}
},
"cveMetadata": {
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"cveId": "CVE-2026-42236",
"datePublished": "2026-05-04T18:38:51.626Z",
"dateReserved": "2026-04-25T05:37:12.117Z",
"dateUpdated": "2026-05-04T19:59:24.621Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
Loading…
Loading…
Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
Loading timeline…
Loading…
Loading…
The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Loading…
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.