---
id: "CVE-2026-62863"
kind: "vulnerability"
aliases: ["CVE-2026-62863"]
title: "MoLing MCP server: browser page can run tool calls over SSE"
severity: "critical"
cvss: 9.6
epss: null
exploited: false
status: "open"
category: "ai-tooling"
products: []
ecosystems: []
tags: ["ai-tooling", "local-dev", "mcp", "mcp-go", "sse"]
not_affected_if: ["stdio-mode", "version-0.5.0-or-later"]
published_at: "2026-10-30T21:17:14+00:00"
first_seen_at: "2026-10-30T21:25:53+00:00"
updated_at: "2026-10-30T21:26:28+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-62863", "first_seen_at": "2026-10-30T21:25:53+00:00"}]
---

# MoLing MCP server: browser page can run tool calls over SSE

MoLing is an MCP server that controls a computer and browser. In SSE mode its endpoints do not check who is calling and send a permissive CORS header, so a malicious web page the user visits can read a session ID and send tool calls that read or write local files or run commands.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed MoLing version; it is affected if it is below `0.5.0`.
- Check whether MoLing was started with the SSE mode flag `-l` (serving `/sse` and `/message`).
- Note that binding to loopback does not prevent the browser-mediated attack.

## Fix

- Upgrade MoLing to `0.5.0` or later.

## Timeline

- 2026-10-30T21:25:53+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-62863

## From the sources

MoLing is a computer-use and browser-use based MCP server. Prior to 0.5.0, when MoLing runs in SSE mode using `-l`, its `/sse` and `/message` HTTP endpoints do not authenticate requests and the `mcp-go` dependency sets `Access-Control-Allow-Origin: *`. A malicious web page can open a cross-origin `EventSource` to `/sse`, including a loopback listener, and read the `endpoint` event to obtain `sessionId`. After a victim running SSE mode visits that page, the attacker can use the disclosed `sessionId` against `/message` to send unauthorized MCP tool calls. Depending on the configured tools, those calls can read or write local files, execute commands or perform other actions. Binding only to loopback does not prevent this browser-mediated attack. This issue is fixed in version 0.5.0.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_