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Luu, T.J.

GHSA-qrx8-25qr-5r7v: n8n: MCP Browser HTTP Transport Exposes Unauthenticated Browser-Control Sessions

highvulnerability

security

Source: GitHub Advisory DatabaseJune 16, 2026CVE-2026-54309

Summary

When n8n's MCP Browser tool runs in HTTP transport mode (a way of sending data over the network), it accepts requests without authentication (verification of identity), meaning anyone on the network or visiting a website can control the user's browser, including navigating to sites, running code, and accessing cookies and stored data. This vulnerability only affects the HTTP transport mode; the default stdio transport (direct computer communication) is safe.

Solution / Mitigation

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. As temporary workarounds while waiting to upgrade: avoid running MCP Browser with HTTP transport and use the default stdio transport instead, or if HTTP transport is necessary, restrict network access to the listening port to trusted clients only using host-based firewall rules. The source notes these workarounds do not fully remediate the risk and should only be used as short-term measures.