@mobilenext/mobile-mcp: Arbitrary Android Intent Execution via mobile_open_url
Summary
The mobile_open_url tool in mobile-mcp passes user-supplied URLs directly to Android's intent system without any scheme validation, allowing execution of arbitrary Android intents, including USSD codes, phone calls, SMS messages, and content provider access.
Details
The vulnerable code passes URLs directly to adb shell am start -a android.intent.action.VIEW -d <url> without checking the URL scheme. This can enable malicious schemes such as tel:, sms:, mailto:, content://, and market:// to be executed.
Since MCP servers are designed to be operated by AI agents, which are vulnerable to prompt injection attacks, a malicious document or website could inject instructions that cause the AI to execute dangerous intents on a connected mobile device.
Impact
An attacker via prompt injection can:
- Execute USSD codes (e.g.,
tel:*#06# to display IMEI - confirmed on Pixel 7a, behavior varies by device; or device-specific factory reset codes) - Initiate phone calls to premium rate numbers
- Draft SMS messages with attacker-controlled content
- Access content providers (contacts, SMS, call logs)
- Open app installation prompts
Proof of Concept
```json
{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"mobile_open_url","arguments":{"device":"<id>","url":"tel:*#06#"}}}
```
Result: IMEI displayed on device.
```json
{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"mobile_open_url","arguments":{"device":"<id>","url":"sms:1234567890?body=HACKED"}}}
```
Result: SMS app opens with a pre-filled message.
Remediation
Upgrade to version 0.0.50 or later, which restricts mobile_open_url to http:// and https:// schemes by default. Users who require other URL schemes can opt in by setting MOBILEMCP_ALLOW_UNSAFE_URLS=1.
