8.8

CVSS Score

4.0

-

CVSS Score

Basic Information

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CVE-2026-54309

CVE-2026-54309: n8n: n8n MCP Browser HTTP Transport Exposes Unauthenticated Browser-Control Sessions

n8n is an open source workflow automation platform. Prior to 2.25.7 and 2.26.2, when @n8n/mcp-browser is run in HTTP transport mode, the MCP endpoint accepts session initialization and tool invocation requests without any authentication. Any network-reachable client, or any website visited by the user, can establish an MCP session and invoke browser-control tools. Where the n8n AI Browser Bridge extension is installed and a browser connection is active, an unauthenticated caller can access browser-control capabilities including navigation, JavaScript evaluation, and cookie and storage access against the user's real browser profile. This issue only affects instances where @n8n/mcp-browser is run with the HTTP transport (--transport http). This vulnerability is fixed in 2.25.7 and 2.26.2.

(GitHub Advisory)

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CVE-2026-54309

CVE-2026-54309:

8.8

CVSS Score

4.0

-

CVSS Score

Basic Information

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Technical Details

SSVC / BOD 26-04 ↗

Exploitation NoneAutomatable YesTech Impact Partial

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Package Name	Ecosystem	Vulnerable Versions	First Patched Version
n8n	npm	>= 2.26.0, < 2.26.2	2.26.2
n8n	npm	< 2.25.7	2.25.7

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability exists because the MCP browser's HTTP transport mode did not require any authentication, allowing unauthenticated access to browser-control capabilities. The analysis of the patch commit reveals that the main function in packages/@n8n/mcp-browser/src/server.ts was responsible for creating an HTTP server with a request handler that lacked any authentication checks. This handler, an anonymous function within createServer, would process any incoming request, making it the vulnerable component. The fix involved a significant refactoring of this file, introducing a new startHttpTransport function that incorporates an authentication check using the newly added isAuthorized function. This function enforces bearer token authentication for all incoming requests to the MCP endpoint. Therefore, the main function (and its anonymous request handler) is identified as the vulnerable function, as it was the entry point for unauthenticated requests in the vulnerable versions.

Vulnerable functions

main

packages/@n8n/mcp-browser/src/server.ts

The `main` function in `packages/@n8n/mcp-browser/src/server.ts` was responsible for setting up the HTTP server. It used an anonymous callback function to handle incoming HTTP requests. This callback function did not perform any authentication or authorization checks, allowing any network-accessible client to establish an MCP session and invoke browser-control tools. The patch introduces bearer token authentication by adding the `isAuthorized` function and checking the token in the new `startHttpTransport` function.

isAuthorized

packages/@n8n/mcp-browser/src/server.ts

This new function was added as part of the fix to implement bearer token authentication. It checks for the `Authorization` header and validates the token. While this function itself is not vulnerable (it's the fix), its absence in the previous version is the core of the vulnerability. Its presence in a runtime profile would indicate a patched version.

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Miggo AI

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WAF Protection Rules

WAF Rule

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Reasoning

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