GHSA-qrx8-25qr-5r7v CVE-2026-54309

n8n: MCP Browser HTTP Transport Exposes Unauthenticated Browser-Control Sessions

Critical npm

Severity: 0.0 / 10; Critical · CVSS 4.0
Exploit chance (EPSS): 0.55%; Chance of exploitation in the next 30 days. Higher than 45.77% of scored vulnerabilities.
Known exploited: No; Not in CISA's catalog
Weakness: CWE-306 Missing Authentication for Critical Function
Fix: 2.26.2; Upgrade n8n to this version or later

Description

Impact

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). The default transport is stdio, which is not affected.

Patches

The issue has been fixed in n8n versions 2.25.7, and 2.26.2. Users should upgrade to one of these versions or later to remediate the vulnerability.

Workarounds

If upgrading is not immediately possible, administrators should consider the following temporary mitigations:

Avoid running @n8n/mcp-browser with the HTTP transport; use the default stdio transport instead.
If HTTP transport is required, restrict network access to the listening port to trusted clients only using host-based firewall rules.

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

Affected versions

npm

Package	Vulnerable	Fixed in
n8n	`>= 2.26.0, < 2.26.2`	`2.26.2`
n8n	`< 2.25.7`	`2.25.7`

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

n8n npm → `2.26.2`

npm

npm install n8n@2.26.2

yarn

yarn add n8n@2.26.2

pnpm

pnpm add n8n@2.26.2

Severity breakdown

CVSS 4.0 0.0

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:L/SC:N/SI:N/SA:N

Attack vector: Network
Attack complexity: Low
Attack requirements: None
Privileges required: None
User interaction: None
Confidentiality (vulnerable system): Low
Integrity (vulnerable system): High
Availability (vulnerable system): Low
Confidentiality (subsequent systems): None
Integrity (subsequent systems): None
Availability (subsequent systems): None

CVSS 3.1 10.0

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:L

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Changed
Confidentiality: High
Integrity: High
Availability: Low

Weakness

CWE-306: Missing Authentication for Critical Function

The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.

How to prevent it

Architecture and Design: Divide the software into anonymous, normal, privileged, and administrative areas. Identify which of these areas require a proven user identity, and use a centralized authentication capability. Identify all potential communication channels, or other means of interaction with the software, to ensure that all channels are appropriately protected, including those channels that are assumed to be accessible only by authorized parties. Developers sometimes perform authentication at the primary channel, but open up a secondary channel that is assumed to be private. For example, a login mechanism may be listening on one network port, but after successful authentication, it may open up a second port where it waits for the connection, but avoids authentication because it assumes that only the authenticated party will connect to the port. In general, if the software or protocol allows a single session or user state to persist across multiple connections or channels, authentication and appropriate credential management need to be used throughout.
Architecture and Design: For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
Architecture and Design: Where possible, avoid implementing custom, "grow-your-own" authentication routines and consider using authentication capabilities as provided by the surrounding framework, operating system, or environment. These capabilities may avoid common weaknesses that are unique to authentication; support automatic auditing and tracking; and make it easier to provide a clear separation between authentication tasks and authorization tasks. In environments such as the World Wide Web, the line between authentication and authorization is sometimes blurred. If custom authentication routines are required instead of those provided by the server, then these routines must be applied to every single page, since these pages could be requested directly.
Architecture and Design: Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, consider using libraries with authentication capabilities such as OpenSSL or the ESAPI Authenticator [REF-45].
Implementation, System Configuration, Operation: When storing data in the cloud (e.g., S3 buckets, Azure blobs, Google Cloud Storage, etc.), use the provider's controls to require strong authentication for users who should be allowed to access the data [REF-1297] [REF-1298] [REF-1302].

References

Advisories

nvd.nist.gov/vuln/detail/CVE-2026-54309

Packages

github.com/n8n-io/n8n

Timeline

Jun 16, 2026 Published
Oct 26, 2026 Last updated by the source
Nov 1, 2026 Latest EPSS score

Advisory	Severity	Why it's related
GHSA-v98v-ff95-f3cp n8n Vulnerable to Remote Code Execution via Expression Injection	High Known exploited	Also affects n8n
GHSA-qgpw-8g46-w95v n8n: Git Node branch.<name>.remote Config Key Bypasses Sandbox Path Restriction, Enabling Local Git Repository Read	Medium	Also affects n8n
GHSA-65xw-2v52-jhxc n8n: Cross-User Active Workflow ID and Lifecycle Event Disclosure via Missing userId Filter	Medium	Also affects n8n
GHSA-pq6c-vh67-xpm3 n8n: Log Streaming Event Destinations Decrypt Generic-Auth Credentials Without Ownership Check	Medium	Also affects n8n
GHSA-cqr2-h44g-v75v n8n: Cross-Tenant Project-Member PII Disclosure via Missing Per-Project Scope Check on Role Assignment Endpoints	Medium	Also affects n8n
GHSA-pf83-w3f9-8m37 n8n: Disabled OIDC SSO Endpoints Remain Active and Issue Valid Sessions	Medium	Also affects n8n
GHSA-6xcw-7xm6-48c6 n8n: Expression Sandbox Escape via Shared Builtin Tampering and Code-Printer Injection Leads to Code Execution	High	Also affects n8n
GHSA-34ff-336r-5q23 n8n: Domain-Restriction Bypass via Unguarded Model-Search Endpoint in OpenAI Chat Model Node	Medium	Also affects n8n

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