Provider-Controlled Metadata -> Plugin Filesystem Traversal

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

provider_metadata_to_filesystem_traversal   HARD

Description

A framework/plugin layer (Flutter/React Native/Cordova/Capacitor) reads DISPLAY_NAME from an UNTRUSTED ContentProvider via ContentResolver.query() and uses it in filesystem path construction with no sanitization, so a malicious provider returns a ../ filename and the plugin writes/reads outside its intended cache - a plugin-boundary traversal where the dangerous code lives behind an innocent-looking app API (Flutter file_picker CVE-2026-38093 class).

How it works

A framework/plugin layer reads DISPLAY_NAME from an untrusted ContentProvider and uses it directly in filesystem path construction with no sanitization. The app author calls an innocent-looking pick() API, but inside the plugin a malicious provider’s “../” display name traverses out of the plugin cache and clobbers the app’s shared_prefs secrets on disk (Flutter file_picker CVE-2026-38093 class). On device this performs a real File(cacheRoot, displayName) write. The secure path takes the basename or canonicalizes the path and confines the write under the plugin cache root.

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: Android: drozer, jadx, adb · iOS: ipsw, class-dump.
2. Locate the target. From the home index, open Provider-Controlled Metadata -> Plugin Filesystem Traversal (provider_metadata_to_filesystem_traversal). 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.

Tools (optional)

Android

• drozer
• jadx
• adb

iOS

• ipsw
• class-dump

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:

• CVE-2026-38093 / GHSA-r2rg-pm28-j8gw (Flutter file_picker DISPLAY_NAME path traversal)