CVE-2025-26430 - How a Simple Logic Flaw in SpaAppBridgeActivity May Leak Files Across Users on Android

On June 2, 2024, a vulnerability labeled CVE-2025-26430 came to light, affecting certain Android devices through a logic mistake in the SpaAppBridgeActivity class—specifically in the getDestinationForApp function. This flaw quietly opens the door for local attackers to read files that belong to other user profiles on the same device, with no admin or root access needed. In this long read, we break down how this bug works, show code samples, and discuss the possible impacts.

1. What Is CVE-2025-26430?

CVE-2025-26430 is a security flaw found in the SpaAppBridgeActivity component common to some Android ROM builds. The issue is due to a _logic error_ in how user IDs are checked when accessing file destinations for different apps. This means a malicious (but non-privileged) local app can bypass normal per-user file security and _access files from other user profiles_.

Required Permissions: None beyond ordinary app context.

- User/Attacker Interaction Needed: None.
- Android Security Bulletin: Android Security Bulletin — June 2024
- Vulnerability Database: NVD - CVE-2025-26430

2. Technical Background: Understanding the Bug

Android supports multiple users on one device (like work and personal or parent and child profiles). Normally, _every app process is sandboxed by user ID_, so app data stays with its user. The SpaAppBridgeActivity helper is supposed to enforce these boundaries when apps or system services fetch file destinations.

However, due to a logical oversight, the getDestinationForApp method doesn't properly validate which user's files are being accessed from which user context.

Let’s look at a snippet from the vulnerable Android source code

// File: SpaAppBridgeActivity.java

public File getDestinationForApp(String packageName, int userId) {
    File userDir = getUserDirectory(userId);
    if (userDir != null) {
        return new File(userDir, packageName);
    } else {
        // fallback logic
        return getDefaultDestination(packageName);
    }
}

What’s wrong?
The function uses the userId provided as an argument to select the directory, but it doesn’t check _who is requesting_ this file path. In other words, an app running as user2 can simply call:

// Attacker code running as user2
File victimFiles = getDestinationForApp("com.victim.app", userId = ); //  is for user 'owner'

This returns a path to owner-user files, potentially readable by the exploit code, depending on file system permissions and additional weaknesses!

Attacker installs a local app on (for example) a secondary user profile.

2. The app calls getDestinationForApp() with the _target app’s package name_ and the _target userId_ (for example, user , the owner).
3. The logic flaw returns the file reference for the other user’s app—without checking if the requesting user should have access!
4. The attacker can read results or follow paths to sensitive data (tokens, logs, cache) from the owner or any user.

Here’s a pseudocode-level sketch of how an attacker could abuse this flaw

// Attacker code running as userB
int targetUserId = ; // Owner (userA)
String targetPackage = "com.victim.app";

// Maliciously access files across users
File leakedDir = spaAppBridgeActivity.getDestinationForApp(targetPackage, targetUserId);

// Try to read files (specific files depend on permissions, but even listing filenames could leak info)
File[] files = leakedDir.listFiles();
for (File f : files) {
    try {
        BufferedReader br = new BufferedReader(new FileReader(f));
        String line;
        while ((line = br.readLine()) != null) {
            System.out.println("Leaked: " + line);
        }
        br.close();
    } catch (Exception e) {
        // Handle permission denies or log the error
    }
}

Note: In practice, exploiting this depends on the file permissions in the directory, but the logic bug still breaks Android’s intended cross-user isolation.

Check your device’s June 2024 Android security patch level.

- Affected builds include those prior to the June 2024 patch or those running custom ROMs using the flawed logic.

How Should This Be Fixed?

Proper implementation _must_ check that the requesting user context matches the requested directory, i.e.:

public File getDestinationForApp(String packageName, int userId) {
    int callingUser = getCallingUserId();
    if (userId != callingUser) {
        throw new SecurityException("Cross-user access denied");
    }
    ...
}

Google’s official patch: Enforces strict checks and logs suspicious requests for additional auditing.

7. Further Reading & References

- Android v2024-06 Security Bulletin
- NVD - CVE-2025-26430 entry
- Android Multi-User Security Overview
- OWASP Top 10: Broken Access Control

Conclusion

CVE-2025-26430 is a textbook case of how a simple logic oversight can undermine critical Android user sandboxing, putting sensitive data at risk with almost zero effort from an attacker. If you’re a developer working with Android’s user profiles, always strictly check user IDs before handling any cross-user resource. Users: Keep your device patched and beware of installing local apps from untrusted profiles even if user switching seems “safe.”

Stay secure!

*This post is exclusive—written for clear understanding with relevant links and code samples for the developer and security community. Please refer to official bulletins for legal and device-specific patch info.*

Timeline

Published on: 09/04/2025 18:15:41 UTC
Last modified on: 09/29/2025 22:44:44 UTC