Exported BroadcastReceiver Data Spoofing

← Native / WebView Bridge (JS <-> Native)

exported_broadcast_receiver_spoof   MEDIUM

Description

An exported BroadcastReceiver accepts broadcasts from any app and trusts their extras, so a local app spoofs data the app treats as authoritative (e.g. device location) (Home Assistant Companion GHSA location-spoof class).

How it works

The app registers a BroadcastReceiver that is exported with no signature-level permission, so any app on the device can send it a broadcast. The receiver trusts the extras it receives as authoritative, a device-location update, and updates app state from them. A local app sends a spoofed LOCATION_UPDATE and the app believes the fake coordinates (Home Assistant Companion GHSA location-spoof class). On Android, the app registers a matching exported receiver; the companion attacker fires the broadcast and this screen reads back the applied extras. The secure path verifies the sender is a trusted first-party package and holds the app’s signature-level permission before applying any extras.

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 Native / WebView Bridge (JS <-> Native) category (e.g. --dart-define-from-file=config/flavors/dev.json) and run on an Android emulator you control. The demo needs no external tooling; for the optional on-device reproduction the relevant tools are: adb, drozer, jadx.
2. Locate the target. From the home index, open Exported BroadcastReceiver Data Spoofing (exported_broadcast_receiver_spoof). 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. Reach the JS<->native bridge (or the framework/plugin API) from untrusted web content / a cross-origin iframe / a malicious provider, and confirm the privileged native call fires with no main-frame/origin, callback-id, or permission gate in between.
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.
6. Map it back. Cross-reference the MASTG v2 test(s) MASTG-TEST-0366 for the canonical procedure and remediation.

Tools (optional)

• adb
• drozer
• jadx

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:

• malicious companion app

Real-world references

Concrete public disclosures that match this vulnerability class:

• GHSA (Home Assistant exported-receiver location spoof)
• CVE-2024-0015 (Android intent redirection to protected activity)