CVE-2026-42235Network attack vector

Session compromise via MCP OAuth client XSS

Published May 4, 2026 · Updated May 4, 2026

Stored XSS in n8n before 1.123.32, 2.17.4, and 2.18.1 allows remote attackers to execute script in authenticated browser sessions. A crafted MCP OAuth client_name is stored and later interpolated into a revocation toast link without adequate neutralization, turning the link into executable JavaScript. Exploitation requires one user to authorize the malicious client, a second user to revoke it, and the first user to click the resulting link; script runs with that user's session and can read credentials or alter workflows.

CVSS severity8.8
High
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in n8n before 1.123.32, 2.17.4, and 2.18.1 allows remote attackers to execute script in authenticated browser sessions. A crafted MCP OAuth client_name is stored and later interpolated into a revocation toast link without adequate neutralization, turning the link into executable JavaScript. Exploitation requires one user to authorize the malicious client, a second user to revoke it, and the first user to click the resulting link; script runs with that user's session and can read credentials or alter workflows.

The record

CVE
CVE-2026-42235
Published
May 4, 2026
Updated
May 4, 2026
Vendor
n8n
Product
n8n
Classifications
CWE-87, CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 4, 2026CVE publishedPublication date reported by the CVE source.
  2. May 4, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.123.32
  2. Affected versionversion=>= 2.17.0, < 2.17.4
  3. Affected versionversion=>= 2.18.0, < 2.18.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

n8n · n8nversion=< 1.123.32; version=>= 2.17.0, < 2.17.4; version=>= 2.18.0, < 2.18.1

Published CVSS scores

8.8GitHub Advisory DatabaseCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-87Improper Neutralization of Alternate XSS Syntax
CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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