Unauthenticated Local / Loopback Service

← Improper Platform Usage

unauthenticated_local_loopback_service   HARD

Description

The app opens a local HTTP/TCP or unix-domain socket (for IPC, a debug bridge, a companion SDK, or a WebView bridge) with no authentication, so any co-resident app - or remote web content via DNS rebinding against 127.0.0.1 - reaches privileged functionality or reads data on that port. The loopback service is treated as trusted merely because it is local. The secure path binds an unpredictable per-session token / origin check to every local request.

How it works

The app opens a privileged service (an IPC, debug, or WebView bridge) on the loopback interface and trusts every caller simply because the socket is “only local”. With no token and no Origin or Host check, a co-resident app can invoke privileged operations, and a remote web page can reach 127.0.0.1 via DNS rebinding and read the app’s secrets. This demo binds a real loopback HTTP server on 127.0.0.1 with no token or Origin check and issues an unauthenticated GET /getSecrets over the socket, recording the exposed response as a pullable artifact. The secure path requires an unpredictable per-session token and validates the Origin and Host, rejecting untokened and rebinding callers.

How to exercise it. DVMA is the harness - open this module from the home index and tap the demo action. The screen ships the malicious input and simulates the attacker (e.g. the companion app, crafted intent, or scanned payload) in-process, and the evidence panel prints the proof. The Tools (optional) and Attack inputs below are only needed to reproduce the exploit end-to-end on a real device.

Exploit steps

1. Set up. Build DVMA with a flavor that enables the Improper Platform Usage category (e.g. --dart-define-from-file=config/flavors/dev.json) and run on an emulator/simulator you control. The demo needs no external tooling; for the optional on-device reproduction the relevant tools are: mitmproxy, Burp Suite, adb, nc, tcpdump.
2. Locate the target. From the home index, open Unauthenticated Local / Loopback Service (unauthenticated_local_loopback_service). The How it works section above describes this module’s specific weakness; the screen states the intended-secure behavior and exposes the vulnerable action.
3. Exploit. From a co-resident/attacker context (adb shell am start/drozer, or a crafted deep link / QR), send the untrusted input to the exported component or WebView and confirm the app performs the unsafe action (navigation, JS execution, file/URI access) with no validation.
4. Observe the evidence. Trigger the vulnerable action and read the evidence panel - it prints the concrete proof (leaked value, accepted replay, executed payload, or unauthorized result).
5. Contrast with the secure path. Run the module’s secure/hardened action (where provided) and confirm the same attack is rejected - this is what a correct implementation should do.

Tools (optional)

• mitmproxy
• Burp Suite
• adb
• nc
• tcpdump

Attack inputs

Payloads/artifacts you author for the on-device attack. The demo already ships and simulates these in-process (e.g. the malicious companion app / crafted intent is emulated inside the screen), so you only need to craft them to reproduce the exploit on a real device:

• localhost request
• DNS-rebinding page

Real-world references

Concrete public disclosures that match this vulnerability class:

• OWASP MASTG: local service exposure and DNS-rebinding against loopback