Security Bypass Affecting microsoft.owin package, versions [,4.1.1)

  • Exploit Maturity

    Proof of concept

  • Attack Complexity


  • Integrity


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  • snyk-id


  • published

    9 Sep 2020

  • disclosed

    8 Sep 2020

  • credit

    Matt Langlois of Github Security Team

How to fix?

Upgrade Microsoft.Owin to version 4.1.1 or higher.


Microsoft.Owin is a Provides a set of helper types and abstractions for simplifying the creation of OWIN components.

Affected versions of this package are vulnerable to Security Bypass. The ASP.NET Core cookie parser decodes entire cookie strings which could allow a malicious attacker to set a second cookie with the name being percent encoded. The security update addresses the vulnerability by fixing the way the ASP.NET Core cookie parser handles encoded names. This CVE also affects Microsoft.Owin due to it using a similar cookie parsing mechanism.