In November 2022, a new vulnerability—CVE-2022-20450—was disclosed by Google affecting multiple versions of Android. This vulnerability allows malicious local apps to escalate their privileges by abusing a missing permission check in the restorePermissionState method of PermissionManagerServiceImpl.java. What's worrying is that user interaction isn’t required for exploitation, and there’s no need for special app privileges—just the vulnerability itself.

Let’s break down what this means, how an attacker might exploit it, and how you can protect yourself.

What Is CVE-2022-20450?

This CVE refers to a logic flaw in the Android operating system's permission management service. Specifically, inside the PermissionManagerServiceImpl.java, the restorePermissionState method lacks a crucial permission check. This opens the door for an attacker with local access (for example, a malicious app you’ve installed) to bypass user consent and grant themselves permissions they shouldn’t have.

This is a classic escalation of privilege vulnerability—letting an unsuspecting app gain more power than the user ever agreed to.

How Does the Vulnerability Work?

The heart of the vulnerability lies in the restorePermissionState function. This is responsible for restoring permission states, typically during app reinstall or device restore operations. Due to a missing permission check, any local app can call this function to restore permissions—effectively granting itself or other apps elevated privileges without user confirmation.

Here’s a simplified look at the vulnerable code (paraphrased for clarity)

// This is a simplified illustration
@Override
public void restorePermissionState(PackageParser.Package pkg, boolean mOrigPermissionGranted, ...)
{
    //... some code ...

    // Missing permission check here!
    final int callingUid = Binder.getCallingUid();

    // Should verify that callingUid is system or has ADMIN permissions, but it doesn't

    // Permission restoration logic...
}

The PROBLEM:
The method should first check if the caller has system-level permissions or verify with an explicit privilege check. Skipping this means any app can trigger this code.

Proof-of-Concept Exploit

Imagine a malicious app with no dangerous permissions initially. But after installation, it calls into the vulnerable method through an IPC (inter-process communication) request.

Pseudo-code for an exploit

// Pseudo-code for exploitation; actual execution might differ
IBinder permMgr = ServiceManager.getService("permissionmgr");
IPermissionManager permissionManager = IPermissionManager.Stub.asInterface(permMgr);

PackageParser.Package targetPkg = ... // target package
permissionManager.restorePermissionState(targetPkg, true, ...);

// Target app now has elevated privileges, without user seeing a prompt.

Note: Actual exploitation in the wild would rely on understanding internal Android services and tailoring calls—but leaked or reverse-engineered exploits could do this.

Patched: Monthly Android Security Bulletin, December 2022 and later versions of Android

Here’s Google’s official Android Security Bulletin (Dec 2022) referencing this CVE.

References

- Android Security Bulletin—December 2022
- CVE-2022-20450 at NVD
- Android Source Code: PermissionManagerServiceImpl.java (AOSP)

Update your device. Make sure it is running the latest security patch (December 2022 or newer).

- Don’t install apps from unknown sources, and avoid sideloading APKs—even from forums promising “pro” versions.

Conclusion

CVE-2022-20450 highlights how a single missing check can compromise the entire user security model. If you’re a user, keep your Android updated. For developers and system designers—never skip secure coding practices.


If you want more technical details, visit the full Android source code diff patch for more insights.

Timeline

Published on: 11/08/2022 22:15:00 UTC
Last modified on: 11/09/2022 14:12:00 UTC