Saml2 Authentication services for ASP.NET (NuGet package Sustainsys.Saml2) greater than 2.0.0, and less than version 2.5.0 has a faulty implementation of Token Replay Detection. Token Replay Detection is an important defence in depth measure for Single Sign On solutions. The 2.5.0 version is patched. Note that version 1.0.1 is not affected. It has a correct Token Replay Implementation and is safe to use. Saml2 Authentication services for ASP.NET (NuGet package Sustainsys.Saml2) greater than 2.0.0, and less than version 2.5.0 have a faulty implementation of Token Replay Detection. Token Replay Detection is an important defense measure for Single Sign On solutions. The 2.5.0 version is patched. Note that version 1.0.1 and prior versions are not affected. These versions have a correct Token Replay Implementation and are safe to use.

Recent assessments:

horshark at March 25, 2020 10:52am UTC reported:

Description

This is a Replay Attack found in versions 2.0.0 to 2.4.0 of “Sustainsys.Saml2” Nuget package.
The attacker can wait for the user’s token to be sent and reuse it.

“The Sustainsys.Saml2 library adds SAML2P support to ASP.NET web sites, allowing the web site to act as a SAML2 Service Provider (SP). The library was previously named Kentor.AuthServices.”

Severity

It depends on the context that the library is being used in. It can grant authentification as another user.
Though getting the token requires high access to the user.

Assessed Attacker Value: 1
Assessed Attacker Value: 1Assessed Attacker Value: 2