MSAL.NET applications targeting Xamarin Android and .NET Android (MAUI) susceptible to local denial of service

[!IMPORTANT] ONLY applications targeting Xamarin Android and .NET Android (MAUI) are impacted. All others can safely dismiss this CVE.

Impact

MSAL.NET applications targeting Xamarin Android and .NET Android (e.g., MAUI) using the library from versions 4.48.0 to 4.60.3 (inclusive, except 4.59.1 and 4.60.3) are impacted by a low severity vulnerability.

A malicious application running on a customer Android device can (1) inject HTML/JavaScript in an embedded web view exported by affected applications, or (2) cause local denial of service against applications that were built using MSAL.NET for authentication on the same device (i.e., prevent the user of the legitimate application from logging in) due to incorrect activity export configuration.

Patches

MSAL.NET version 4.60.3 includes the fix. We recommend all users of MSAL.NET that are building public client applications for Android update to the latest version.

Workarounds

We recommend developers update to the latest version of MSAL.NET. If that is not possible, a developer may explicitly mark the MSAL.NET activity non-exported:

<activity android:name="microsoft.identity.client.AuthenticationAgentActivity" android:configChanges="orientation|screenSize" android:exported="false">
<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="msalYOUR_CLIENT_ID" android:host="auth" />
</intent-filter>
</activity>

References

Refer to MSAL.NET documentation for latest guidance and best practices on configuring client applications using the library.