System Assistant -> Locked-Device Capability Abuse

← Privacy (OWASP Mobile M6)

assistant_locked_device_capability_abuse   MEDIUM

Description

The system assistant surface (Siri / App-Intents / voice shortcuts) exposes sensitive information or performs a privileged capability while the device is LOCKED because the assistant path never re-checks authentication, so a physical attacker reads protected data or triggers an action without unlocking (iOS Siri locked-device disclosure CVE-2026-28856 class).

How it works

The system assistant (Siri / App-Intents / a voice shortcut) exposes sensitive information or performs a privileged capability while the device is locked because the assistant invocation path never re-checks the keyguard. An attacker holding a locked phone triggers the assistant to read the account balance aloud without ever unlocking. This is the assistant / voice-intent surface specifically. On iOS the assistant path is backed by a real App Intent (UnlockFrontDoorIntent) shipped in the app binary that declares no authentication policy, so Siri / App Intents run it from a locked device; off-iOS it uses a deterministic model. The secure path re-checks the lock state on the assistant path and requires unlock/authentication for sensitive capabilities, returning only non-sensitive results while locked.

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 Privacy (OWASP Mobile M6) category (e.g. --dart-define-from-file=config/flavors/dev.json) and run on an iOS simulator / a device you control. The demo needs no external tooling; for the optional on-device reproduction the relevant tools are: Siri.
2. Locate the target. From the home index, open System Assistant -> Locked-Device Capability Abuse (assistant_locked_device_capability_abuse). 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. Trigger the data-access/telemetry path and confirm sensitive data is collected, transmitted, or associated without the required consent / transparency prompt.
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)

• Siri

Real-world references

Concrete public disclosures that match this vulnerability class:

• CVE-2026-28856 (iOS Siri locked-device sensitive-information disclosure)