GHSA-537J-GQPC-P7FQ

Vulnerability from github – Published: 2026-04-29 21:23 – Updated: 2026-05-08 01:31
VLAI?
Summary
n8n Vulnerable to XSS via MCP OAuth client
Details

Impact

An unauthenticated attacker could register a malicious MCP OAuth client with a crafted client_name. If a victim user authorized the OAuth consent dialog and a second user subsequently revoked that access, a toast notification would render the injected script. Clicking the link would execute arbitrary JavaScript in the victim's authenticated n8n browser session, enabling credential and session token theft, workflow manipulation, or privilege escalation.

Patches

This issue has been fixed in n8n version 2.14.2. Users should upgrade to this version or later to remediate the vulnerability.

Workarounds

If upgrading is not immediately possible, administrators should consider the following temporary mitigations: - Restrict access to the n8n instance and the MCP OAuth registration endpoint to trusted users only. - Disable MCP server functionality if it is not actively required.

These workarounds do not fully remediate the risk and should only be used as short-term mitigation measures.

Severity ?
8.2 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:L
8.8 (High)
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L
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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "n8n"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.123.32"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "n8n"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.18.0"
            },
            {
              "fixed": "2.18.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "n8n"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.17.0"
            },
            {
              "fixed": "2.17.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-42235"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79",
      "CWE-87"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-29T21:23:04Z",
    "nvd_published_at": "2026-05-04T19:16:06Z",
    "severity": "HIGH"
  },
  "details": "## Impact\nAn unauthenticated attacker could register a malicious MCP OAuth client with a crafted `client_name`. If a victim user authorized the OAuth consent dialog and a second user subsequently revoked that access, a toast notification would render the injected script. Clicking the link would execute arbitrary JavaScript in the victim\u0027s authenticated n8n browser session, enabling credential and session token theft, workflow manipulation, or privilege escalation.\n\n## Patches\nThis issue has been fixed in n8n version 2.14.2. Users should upgrade to this version or later to remediate the vulnerability.\n\n## Workarounds\nIf upgrading is not immediately possible, administrators should consider the following temporary mitigations:\n- Restrict access to the n8n instance and the MCP OAuth registration endpoint to trusted users only.\n- Disable MCP server functionality if it is not actively required.\n\nThese workarounds do not fully remediate the risk and should only be used as short-term mitigation measures.",
  "id": "GHSA-537j-gqpc-p7fq",
  "modified": "2026-05-08T01:31:29Z",
  "published": "2026-04-29T21:23:04Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/n8n-io/n8n/security/advisories/GHSA-537j-gqpc-p7fq"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-42235"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/n8n-io/n8n"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:L",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L",
      "type": "CVSS_V4"
    }
  ],
  "summary": "n8n Vulnerable to XSS via MCP OAuth client"
}


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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.



Detection rules are retrieved from Rulezet.