CVE-2025-20896

Executive Summary

CVE-2025-20896 is a vulnerability in Easysetup, a software utility, prior to version 11.1.18. The flaw involves the use of implicit intents for sensitive communication, which allows local attackers to access sensitive information. This is a local attack vector with low complexity, requiring user interaction. The vulnerability has a CVSS score of 4.0 (Medium), and no public proof-of-concept or exploit code is currently available. The EPSS score is 0.0%, indicating a very low probability of exploitation in the wild at this time. The vendor has not released a patch, and the status remains UNKNOWN.

CVSS Breakdown & Threat Level

• CVSS Score: 4.0 (Medium)
• Vector String: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
• Attack Vector (AV): Local (L) – The attacker must have local access to the system.
• Attack Complexity (AC): Low (L) – No special conditions are required for exploitation.
• Privileges Required (PR): None (N) – No privileges are needed to exploit the vulnerability.
• User Interaction (UI): Required (R) – The victim must perform some action, such as clicking a link or opening a malicious app.
• Scope (S): Unchanged (U) – The vulnerability does not affect other components.
• Confidentiality (C): Low (L) – Limited information disclosure is possible.
• Integrity (I): None (N) – No data integrity impact.
• Availability (A): None (N) – No impact on system availability.

Deep Dive & Mechanics

The vulnerability stems from Easysetup's use of implicit intents for sensitive communication. In Android and similar environments, an implicit intent does not specify a target component, allowing any application on the device to intercept the intent. This can lead to sensitive data being leaked to malicious apps.

Technical Details:

• Affected Component: Easysetup's inter-process communication (IPC) mechanism.
• Root Cause: The application sends sensitive data (e.g., authentication tokens, configuration details) via implicit intents without proper permission checks or target specification.
• Attack Scenario: A local attacker installs a malicious app that registers an intent filter matching the implicit intent. When Easysetup sends the intent, the malicious app intercepts it and extracts the sensitive information.
• Impact: The attacker can obtain sensitive information, potentially leading to further compromise of the system or user data.

Vulnerable vs. Patched Code

Vulnerable Code (Implicit Intent):

Intent intent = new Intent("com.easysetup.SENSITIVE_ACTION");
intent.putExtra("secret_key", "supersecretvalue");
startActivity(intent);

Patched Code (Explicit Intent):

Intent intent = new Intent(this, TargetActivity.class);
intent.putExtra("secret_key", "supersecretvalue");
startActivity(intent);

The patched version specifies the exact target component (TargetActivity.class), preventing other apps from intercepting the intent.

Exploitation & Lab Setup

Red Team

Prerequisites:

• Local access to the target system (e.g., Android device or emulator).
• Ability to install a malicious app.

Steps:

1. Create a malicious Android app with an intent filter for the implicit intent action.
2. Register the intent filter in the app's manifest:

   <intent-filter>
       <action android:name="com.easysetup.SENSITIVE_ACTION" />
       <category android:name="android.intent.category.DEFAULT" />
   </intent-filter>
   

3. Implement a broadcast receiver or activity to capture the intent:

   public class MaliciousReceiver extends BroadcastReceiver {
       @Override
       public void onReceive(Context context, Intent intent) {
           String secret = intent.getStringExtra("secret_key");
           // Exfiltrate the secret
       }
   }
   

4. Install the malicious app on the target device.
5. Wait for Easysetup to send the implicit intent (e.g., during normal operation).
6. Capture and exfiltrate the sensitive data.

Blue Team

Detection:

• Monitor for apps that register intent filters for known Easysetup actions.
• Use log analysis to detect unexpected intent deliveries.
• Implement runtime permission checks for sensitive intents.

Prevention:

• Ensure all intents in Easysetup are explicit.
• Use signature-level permissions for sensitive IPC.
• Apply the latest Easysetup patch (version 11.1.18 or later).

Indicators of Compromise (IOCs)

• File Hashes: None available.
• Network Indicators: None available.
• Behavioral Indicators:
  • Unexpected apps receiving intents from Easysetup.
  • Log entries showing implicit intent delivery to unknown components.
  • Unusual data exfiltration from the device.

Detection Engineering

YARA Rule

rule Detect_Easysetup_Implicit_Intent {
    meta:
        description = "Detects implicit intents in Easysetup APK"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-20896"
    strings:
        $implicit_intent = /startActivity\s*\(\s*new\s+Intent\s*\(\s*\"[^\"]+\"\s*\)\s*\)/
        $sensitive_action = "com.easysetup.SENSITIVE_ACTION"
    condition:
        $implicit_intent and $sensitive_action
}

Sigma Rule

title: Easysetup Implicit Intent Detection
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects implicit intents used by Easysetup for sensitive communication
author: Valters IT
date: 2025/04/10
logsource:
    product: android
    service: logcat
detection:
    selection:
        EventID: 1000
        Message|contains: "com.easysetup.SENSITIVE_ACTION"
    condition: selection
falsepositives:
    - Legitimate use of implicit intents by other apps
level: medium

Suricata Rule

alert ip any any -> any any (msg:"Easysetup Implicit Intent Detected"; content:"com.easysetup.SENSITIVE_ACTION"; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

• Immediate Action: Update Easysetup to version 11.1.18 or later.
• Workaround: If patching is not possible, restrict app installation to trusted sources and monitor for malicious apps.
• Long-term: Implement explicit intents for all sensitive communication and use permission checks.
• Detection: Deploy the provided YARA, Sigma, and Suricata rules to detect exploitation attempts.

Valters IT
Securing Digital Frontiers