Third-Party Authenticator / Cross-Device Pairing Authorization Missing

← Insecure Authentication / Authorization

passkey_thirdparty_pairing_authz   HARD

CategoryInsecure Authentication / Authorization
OWASP Mobile (2024)M3
MASVSMASVS-AUTH-2MASVS-PLATFORM-1
MASWEMASWE-0020
CWECWE-862CWE-306
PlatformAndroidiOS

Description

Third-party authenticator / cross-device passkey-entry pairing is approved without a permission/authorization check, so an unauthorized app or device is paired for passkey entry (Android CVE-2025-48640 / BLE passkey-entry CVE-2026-65935 class).

How it works

The pairing broker auto-approves any third-party authenticator or cross-device requester with no allow-list, permission, or consent check, so a rogue app or device is paired for passkey entry. A correct broker requires an allow-listed requester, the pairing permission, and explicit user consent. Scope: the FIDO2 signature is assumed valid (signature verification is out of scope); the flaw demonstrated is in the relying-party authorization logic on top of it.

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 Insecure Authentication / Authorization 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: webauthn test harness, mitmproxy · Android: adb, drozer · iOS: xcrun simctl openurl, idb.
  2. Locate the target. From the home index, open Third-Party Authenticator / Cross-Device Pairing Authorization Missing (passkey_thirdparty_pairing_authz). 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. Drive the authentication/authorization path, capture the token / assertion / decision, then replay or tamper with it (mitmproxy, a WebAuthn test harness, or by editing the value) and confirm the server-side check accepts the manipulated request.
  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

iOS

Real-world references

Concrete public disclosures that match this vulnerability class: