A new Android security vulnerability, CVE-2025-22439, has drawn serious attention due to its potential to let apps bypass storage access restrictions. The flaw stems from a missing permission check in the onLastAccessedStackLoaded method of ActionHandler.java. This makes it possible for a malicious app to access data from other apps without proper approval. While user interaction is required for exploitation, no special execution privileges are needed, meaning any user-installed app could take advantage of this bug if manipulated correctly.

In this post, we'll break down the vulnerability in plain language, show you where the code went wrong, and explain how attackers might exploit the issue. We'll also provide reference links to original advisories and discuss mitigation steps you can take.

What’s the Problem?

Android uses storage restrictions to protect your personal data. Normally, an app must ask your permission to access files or folders outside its sandbox (private directory). However, CVE-2025-22439 found a loophole in how Android manages access to shared storage stacks. The bug lives in a system component called ActionHandler.java, which is responsible for handling storage actions.

Here's the basic flow

- When an app requests to access stack data (a group of files, or "stack"), the system should check if it’s allowed.

However, a key permission check is missing in this process.

- This can let a rogue app trick the system into giving access to files it shouldn’t see, simply by taking advantage of how the data is loaded after being "last accessed."

Let's look at a simplified snippet inspired by the vulnerable method

// ActionHandler.java

public void onLastAccessedStackLoaded(Stack stack) {
    // Missing: Permission check for app trying to access the stack

    // The following code executes regardless of caller's privileges
    Intent intent = new Intent(ACTION_VIEW_STACK);
    intent.putExtra(EXTRA_STACK, stack);
    context.startActivity(intent);
}

What's wrong?
The method should confirm that the caller has permission to use the stack’s data. Instead, it moves right ahead and launches an activity using the sensitive data, opening the door for cross-app access.

Preparation:

The attacker builds a simple app and baits the user into running a function that simulates a legitimate storage-related feature (e.g., a file manager utility).

Trigger the Vulnerability:

The app calls the vulnerable onLastAccessedStackLoaded method, requesting a data stack it shouldn't have.

Bypass Restrictions:

Due to the missing permission check, the method proceeds and grants access, exposing files/folders belonging to another app or user space.

4. Access/Exfiltrate Data:

Impact:

Sensitive data—including private app data, documents, or media—can be seen or tampered with by a malicious app. This is local privilege escalation: the attacking app gains higher privileges than it's supposed to have.

Why User Interaction is Required

The exploit still needs some user interaction. For instance, the user may have to click a button or grant a basic permission (like allowing the file manager utility to browse files), which isn't unusual in many apps. But *no* special Android permissions—like root or developer privileges—are required.

References

- NVD: CVE-2025-22439 Details *(official advisory, check for updates)*
- Android Security Bulletin - June 2025
- Permission Checking in Android

Mitigation

For users:

Avoid granting file access permissions to apps you don’t completely trust.

For developers:

Review permission enforcement in storage access flows.

- Always perform explicit permission checks before giving access to sensitive resources—don’t assume a system component will do this for you.

Watch for updates to Android SDKs and follow security advisories.

For device vendors:

Exclusive Takeaway

CVE-2025-22439 highlights how a *single missing line of code* can undermine strong system-wide security policies. The Android storage model is complex, and even system-managed components require frequent security audits.

Developers, always check permissions—every time, everywhere.


If you want to track this vulnerability and ensure you’re protected, follow the official Android security bulletins and apply all updates as soon as they’re released. This is especially critical due to the widespread impact and minimal user interaction required.

Stay safe—permission checks are everyone's business.


*Exclusive for security enthusiasts:
If you have a test environment, try scanning code for missing permission checks in public system components—you might spot more issues before bad actors do.*


Learn more about Android security best practices ➔

Timeline

Published on: 09/02/2025 23:15:35 UTC
Last modified on: 09/04/2025 16:37:34 UTC