In early 2025, security researchers discovered a potentially serious issue within the VpnManager.java component of the Android platform. Tracked as CVE-2025-26424, this vulnerability could allow one user on an Android device to access VPN data belonging to another user, thanks to a simple—yet critical—logic error. This post breaks down the flaw, shows you exploitable code, and shares how the vulnerability could be abused.

What is CVE-2025-26424?

This vulnerability exists in how the VpnManager service checks (or fails to check) Android user context before returning sensitive VPN session data. It allows a lower-privilege, local Android user (like a restricted user or guest) to read VPN settings or status attached to another user profile on the same device.

Where’s the Problem? (Code Breakdown)

At its heart, the bug is caused by not verifying which user is making a request against which VPN session. Here’s a code illustration based on the VpnManager.java logic in recent Android versions (source: AOSP VpnManager.java):

public class VpnManager extends SystemService {
    // ...

    public VpnInfo getVpnInfo() {
        // FLAW: Using getCallingUserId() without checking if it's the current user.
        return vpnService.getVpnInfo(getCallingUserId());
    }
}

The intended behavior is for only the current active user to query their own session info. But, if a malicious local app or user switches users at just the right moment and manages to call this API, the check may return data for another profile.

Exploitable Logic

public VpnInfo getVpnInfo(int userId) {
    // Does not enforce userId == current profile!!
    return vpnInfoMap.get(userId); // Returns details for *any* user!
}

How an Attacker Could Use It

Any local user with the ability to run code (e.g., installed app, shell access) could call into the VpnManager API and specify a userId for another profile on the device:

// Pseudo-code exploit example
VpnManager vpnManager = context.getSystemService(VpnManager.class);
for (int userId : getDeviceUserIds()) {
    VpnInfo info = vpnManager.getVpnInfo(userId);
    // exfiltrate or log VPN info here!
}

Connection status

- Potentially IP addresses or usage data (depends on implementation/version)

“Owner” user profiles when sharing device with guests or kids

- Enterprise/work profiles on BYOD (bring your own) phones

Realistic Exploit Scenario

Imagine an Android tablet in a home, with a “kids” profile and the parent’s owner profile. The parent uses a VPN app. A clever app (requiring no special permissions) installed in the kids’ profile could, via the public VpnManager APIs, request and receive details about the parent’s VPN sessions—without root, exploits, or even any malicious interaction.

References and Further Reading

- Android Issue Tracker entry

*(When public, for status and patch details.)*

- AOSP VpnManager.java source code
- Android Security Release Notes - June 2025 *(Look for CVE-2025-26424)*

Remediation

Google is addressing this in the June 2025 Android security update. Device makers should patch their versions of VpnManager.java to include robust user-context checks like:

if (userId != getCurrentUserId()) {
    throw new SecurityException("Cross-user access denied!");
}

Limit device sharing with untrusted users until patched.

- Enterprises: Deploy updates to any managed fleet, especially with user/work profiles.

Bottom Line

CVE-2025-26424 is a classic, easy-to-miss logic bug with big consequences: leaking sensitive VPN information across profiles. If you ever thought, “Local bugs can’t be as bad as remote” — this is a reminder that data separation is just as important on shared devices. Always update, always review code for logic errors—not just crashes or buffer overflows!

Stay safe, and keep coding secure!

*This post is for educational purposes only. Exploiting this or similar vulnerabilities on devices you do not own is illegal and unethical.*

Timeline

Published on: 09/04/2025 18:15:40 UTC
Last modified on: 09/05/2025 19:11:21 UTC