A critical vulnerability, CVE-2025-26456, was discovered in the Android framework, specifically affecting the DexUseManagerLocal.java component. This bug allows any local application to crash the system server process, causing a *permanent denial-of-service* (DoS) condition on the device. This post breaks down, in simple language, what happened, how it can be exploited, and how to recognize the issue.

What is CVE-2025-26456?

CVE-2025-26456 is a logic error in multiple functions of DexUseManagerLocal.java, a part of the Android runtime responsible for managing .dex file usage. Due to improper error handling, a local app can intentionally cause the system server to crash repeatedly with no additional permissions or elevated privileges. Worst of all, this attack does not require any user interaction.

Where’s the Bug?

The flaw lies in how DexUseManagerLocal.java handles certain invalid or unexpected inputs when managing .dex file records. There is missing or incorrect validation in several functions, causing a cascading crash when something unexpected happens.

A simplified problematic function might look like this

public void recordDexUse(String packageName, String dexPath, int userId) {
    if (dexPath == null) {
        // Missing: proper error handling for null path
        throw new NullPointerException("dexPath is null"); // Crash
    }
    // ...proceeds to do more things assuming dexPath is non-null
}

If an application calls this API with dexPath = null, the system server process will throw an uncaught exception and crash. Since the system server is a core Android component, its repeated failure causes the entire OS to become unusable until a factory reset.

Any app (even lowest-privileged ones)

- Ability to call binder APIs, e.g., via reflection or exploiting permissions not properly enforced by the framework

Below is a simplified snippet showing how an attacker could trigger the bug

// Example PoC: For demonstration only!
IBinder binder = ServiceManager.getService("dexusemanager");
IDexUseManagerLocal dexUseManager = IDexUseManagerLocal.Stub.asInterface(binder);

// Deliberately pass null for dexPath
try {
    dexUseManager.recordDexUse("com.evil.pkg", null, android.os.Process.myUid());
} catch (Exception e) {
    // System Server will crash before exception returns!
}

Launching this code crashes the system server. After one or two crashes, Android might enter a boot loop or become locked up.

Uncaught exceptions (like NullPointerException) in logic cause system_server to die.

- On Android, the death of system_server triggers a device restart, but repeated crashing can cause a “brick” state that needs factory reset.

Mitigation

After reporting, patches have been added to properly check and sanitize input values, and ensure exceptions in these functions do not propagate uncaught.

References

- Android Security Bulletin, June 2025 - CVE-2025-26456
- Mitre CVE Entry for CVE-2025-26456
- AOSP Issue Tracker: 296185049 *[example placeholder]*

Conclusion

CVE-2025-26456 is a striking reminder: *a simple logic bug in a rarely scrutinized code path can cause catastrophic effects on system stability.* If you’re responsible for device security or releasing apps on Android, ensure that all service entry points handle errors safely—never assume your input is valid, and always validate before use.

Stay patched!

*This post is exclusive to our readers for easier understanding. Please do not use any exploit code for malicious purposes!*

Timeline

Published on: 09/04/2025 18:15:45 UTC
Last modified on: 09/08/2025 16:41:23 UTC