Platform-Version Security Fallback

← Improper Platform Usage

platform_version_security_fallback   MEDIUM

Description

A security decision is gated on the OS version (if (SDK_INT >= X) / @available) and silently falls back to an INSECURE path on older versions - e.g. skipping StrongBox/hardware-key backing, biometric class checks, or a network-security-config protection - so devices below the threshold run without the protection the code appears to provide. The secure path fails closed (refuses the sensitive op) when the platform can’t provide the guarantee (Android/iOS version-fallback class, MASTG-TEST-0245).

How it works

A security decision is gated on the OS version (an SDK_INT or @available check) and silently falls back to an insecure path on older versions. Here, storing a key with hardware backing (StrongBox or the Secure Enclave) requires a newer API level; on an older OS the code quietly stores the key in software or plaintext and proceeds as if it were protected, so devices below the threshold run without the guarantee (MASTG-TEST-0245 class). This is an offline, deterministic simulation. The secure path fails closed, it refuses the sensitive op when the platform cannot provide the hardware guarantee, and stores hardware-backed only on a supported OS.

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: jadx · iOS: ipsw, Hopper.
2. Locate the target. From the home index, open Platform-Version Security Fallback (platform_version_security_fallback). 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.
6. Map it back. Cross-reference the MASTG v2 test(s) MASTG-TEST-0245 for the canonical procedure and remediation.

Tools (optional)

• jadx

iOS

• ipsw
• Hopper

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:

• older-OS runtime

Real-world references

Concrete public disclosures that match this vulnerability class:

• OWASP MASTG-TEST-0245: references to platform version APIs (security fallback)