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Auth0 Security Bulletin CVE-2019-7644

Published: February 15, 2019

CVE number: CVE-2019-7644

Credit: Conny Dahlgren, Security Researcher at DevilSec AB

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All versions of Auth0-WCF-Service-JWT NuGet package lower than 1.0.4 include sensitive information about the expected JWT signature in an error message emitted when JWT signature validation fails:

This vulnerability allows attackers to use this error message to obtain a valid signature for arbitrary JWT tokens. This way attackers can forge tokens to bypass authentication and authorization mechanisms.

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Am I affected?

You are affected by this vulnerability if the following conditions apply:

  • You use a version of Auth0-WCF-Service-JWT NuGet package lower than 1.0.4
  • You show signature verification exception message in the user interface or make it otherwise available to the attacker (for example through logs or diagnostic messages)

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How to fix that?

Developers using the Auth0-WCF-Service-JWT library need to upgrade to the latest version 1.0.4.

The updated package is available on NuGet:

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Will this update impact my users?

No. This fix patches the library that your application runs, but will not impact your users, their current state, or any existing sessions.