CVE-2025-22431 - How a Logic Bug Lets Malicious Apps Block Emergency Dialing (DoS Exploit Deep Dive)

In June 2025, security researchers discovered a serious flaw affecting emergency service dialing on certain Android devices. Tracked as CVE-2025-22431, the bug allows a malicious app to block calls to 911 or 112—causing a local Denial of Service (DoS) without needing extra permissions, or even user interaction. This isn’t a typical Android bug: it’s a logic error buried in the system that impacts user safety.

In this article, we’ll break down the vulnerability, explore a code snippet illustrating the bug, and walk through a hypothetical exploit scenario. We’ll also link to references for further reading.

What’s the Issue?

CVE-2025-22431 happens when certain Android code paths incorrectly handle phone lock states and call routing. Under uncommon—but realistic—circumstances, a malicious app can hijack the emergency dialing flow so no outgoing emergency call can reach dispatchers until you reboot the device.

Why Does This Matter?

Blocking emergency calls can risk lives, especially if a user has no idea why calls aren’t going through. Unlike many exploits, this one does not require user action like opening the app or clicking links. No extra Android permissions are needed. Installing the app is enough.

Here’s a simplified version of the flawed code logic (not real source, but a close example)

// In some emergency call handler
if (!isDeviceLocked()) {
    processOutgoingCall(intent);
} else {
    if (!isEmergencyNumber(intent.getNumber())) {
        showLockedNotification();
        return;
    }
    // SHOULD process emergency call here, but due to logic error:
    if (shouldBlockAllCalls()) {
        dropCall();
        return;
    }
    processOutgoingCall(intent);
}

Problem: Under certain conditions (shouldBlockAllCalls() returning true), the emergency call gets dropped, even if it’s to 911 or 112. The correct logic should always allow emergency calls.

Real-World Exploitation Path

An attacker creates an app that keeps the device in a specific "locked" state and triggers shouldBlockAllCalls() to return true. When a real emergency arises, the phone refuses to dial emergency numbers. Victims won’t know the problem until after a reboot; there’s no popup, no warning.

Below is a simplified Android service that would “lock” call routing and exploit the bug

public class EmergencyLockdownService extends Service {
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        // Locks phone call routing by triggering buggy state
        createFakeSystemConditionThatAbusesCVE();
        return START_STICKY;
    }

    private void createFakeSystemConditionThatAbusesCVE() {
        // Triggers edge-case logic
        SystemProperties.set("abuser.emergency_do_block", "true");
        // This property forces shouldBlockAllCalls() path in above pseudo logic
    }

    // ... standard Service boilerplate ...
}

Note: Real-world abuse would likely use hidden flags, deeper hooks, or manipulate system broadcasts.

How Did this Happen?

The error started with a good intention: blocking calls when the phone is in a compromised, locked, or high-risk state. But, developers forgot to always allow emergency numbers, no matter what. Attackers realized they could manipulate the phone into this logic trap.

Reboot your phone if you suspect any emergency calling issue.

- Report any failures to dial 911/112 to your device maker.

Official References

- NVD Entry for CVE-2025-22431
- Android Security Bulletin June 2025

Conclusion

Logic errors in critical system flows like emergency calling can have drastic results—sometimes endangering life. CVE-2025-22431 reminds us that “default deny” must always make exceptions for true life-and-death needs. Make sure your devices are up to date, and always watch for security advisories!


> _If you found this breakdown useful, share it with your IT team or device administrator. Stay safe!_

Timeline

Published on: 09/02/2025 23:15:34 UTC
Last modified on: 09/04/2025 16:39:07 UTC