In early 2025, a significant Android security vulnerability emerged and was tracked as CVE-2025-22437. This flaw resides in the handling of media button events within setMediaButtonReceiver routines, present across multiple system and third-party files. With just a minor logic error, hostile apps running in the background can trigger arbitrary activities—even privileged ones—without needing extra permissions or any user action. This article breaks down how easy it is for attackers to exploit this, including code snippets and direct links to referenced materials.

What is setMediaButtonReceiver?

In Android, the setMediaButtonReceiver method is used by apps and services to listen or respond to hardware media button events (like play, pause, next, etc.). Traditionally, only foreground or explicit components are supposed to respond, and launching activities from the background is heavily restricted for security.

However, due to a logic oversight, multiple system files—including certain versions of the Android MediaSession framework—fail to properly check the calling state. This means a background process can inject its own Activity launch intent, bypassing normal restrictions.

Let’s check a simplified, vulnerable version of the code

public void setMediaButtonReceiver(PendingIntent receiver) {
    // ...other code...
    if (receiver != null) {
        Intent mediaIntent = new Intent(Intent.ACTION_MEDIA_BUTTON);
        mediaIntent.setPackage(context.getPackageName());

        // LOGIC BUG: no check if PendingIntent resolves to an Activity,
        // and no foreground/background check
        receiver.send(context, , mediaIntent);
    }
}

How Attackers Exploit the Bug

Let’s see how a malicious app would exploit this.

1. Create a PendingIntent that wraps an intent for any Activity they wish (even one from a privileged app, if exported).

Register this PendingIntent with a vulnerable setMediaButtonReceiver call.

3. Trigger media button handling, often by faking a media button event, and the system will process the PendingIntent, blindly launching the attacker-chosen Activity—as the system user!

Proof-of-Concept Snippet (Attacker’s App)

// MaliciousApp.java
Intent attackIntent = new Intent();
attackIntent.setComponent(new ComponentName("com.android.settings", "com.android.settings.Settings$WifiSettingsActivity")); // Could be any exported Activity

PendingIntent evilPending = PendingIntent.getActivity(context, , attackIntent, PendingIntent.FLAG_IMMUTABLE);

MediaSession session = new MediaSession(context, "EvilSession");
session.setMediaButtonReceiver(evilPending); // Passes the dangerous PendingIntent to vulnerable code

With that, the attacker can launch any exported Activity—including those performing sensitive actions. Since no user interaction is needed, this can happen silently in the background.

Escalating Privileges

Although the app does not need special permissions, by launching activities like Wi-Fi settings or system dialogs that are exported but not intended for direct access, attackers can trick the system into leaking data or altering state—a classic local privilege escalation.

In certain OEM Android versions, some system Activities had misconfigured intents, allowing further escalation, wiping accounts, toggling network, or even accessing hidden system menus.

Potential to access system-level features via exported Activities.

This breaks the Android security model, which tries to tightly limit what background apps can do.

Example Scenario

Suppose a malicious podcast app is running in the background. The attacker registers a PendingIntent that opens the "Add Account" screen in system settings. Suddenly, the account setup pops up over whatever the user is doing—no notification, no forewarning.

On some devices, attackers could chain this with accessibility service exploits (if the user had previously enabled their service) to complete actions on the user’s behalf.

How to Patch

The fix is straightforward: check the PendingIntent type and ensure the component launched is safe and the app is foregrounded.

Reference patch

if (receiver != null) {
    // Defensive: only allow foreground, check intent type
    if (!isAppInForeground(context) || !isSafePendingIntent(receiver)) {
        Log.w(TAG, "Denied unsafe setMediaButtonReceiver");
        return;
    }
    receiver.send(context, , mediaIntent);
}

Here, isAppInForeground and isSafePendingIntent would contain logic to prevent accidental elevation.

References

- Official CVE Record: CVE-2025-22437
- Android Open Source Project Security Bulletins
- Android Developers: PendingIntent Security Considerations

Conclusion

CVE-2025-22437 is a textbook example of why even small logic errors can become big security holes. Letting any PendingIntent launch any Activity without checking the calling context can undermine entire layers of platform protection. Update your device, check your apps, and if you’re a developer, never assume an Intent is safe—always verify sender, type, and permissions.

*Stay tuned for more security analysis and always patch early!*

Timeline

Published on: 09/02/2025 23:15:34 UTC
Last modified on: 09/04/2025 16:37:56 UTC