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Fragment Injection

Description​

The application is vulnerable to Fragment Injection caused either by an unsafe implementation of PreferenceActivity or an insecure configuration of isValidFragment.

Impact​

Use malicious fragments to exploit different vulnerabilities.

Recommendation​

  • Set the attribute exported to false to avoid the attempt of foreign applications to exploit the vulnerability.
  • Ensure the application is running with targetSdkVersion higher than 19.
  • Set a whitelist of trusted fragments and validate them through the implementation of isValidFragment.

Threat​

Authenticated attacker from the Internet.

Expected Remediation Time​

⌚ minutes.

Score​

Default score using CVSS 3.1. It may change depending on the context of the src.

Base​

  • Attack vector: N
  • Attack complexity: H
  • Privileges required: L
  • User interaction: N
  • Scope: U
  • Confidentiality: N
  • Integrity: L
  • Availability: N

Temporal​

  • Exploit code madurity: P
  • Remediation level: O
  • Report confidence: R

Result​

  • Vector string: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N/E:P/RL:O/RC:R
  • Score:
    • Base: 3.1
    • Temporal: 2.7
  • Severity:
    • Base: Low
    • Temporal: Low

Compliant code​

Implement a check for every fragment introduced to the application

public boolean isValidFragment(String fragmentName) {
  return MyFragment.class.getName().equals(fragmentName);
}

Non compliant code​

There are unverified inputs that are used to put fragments into the application

@Override
String initialFragment = getIntent().getStringExtra(EXTRA_SHOW_FRAGMENT);
Bundle initialArguments = getIntent().getBundleExtra(EXTRA_SHOW_FRAGMENT_ARGUMENTS);
if (savedInstanceState != null) {
  //Handle Exception
} else {
    if (initialFragment != null && mSinglePane) {
      // Add Fragment to the application
    }
  }
}

Requirements​

Fixes​

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