Anders Abel

The Sustainsys.Saml2 library incorrectly treats all incoming tokens as bearer tokens, even though they have another subject confirmation method specified. This could be used by an attacker that could get access to Saml2 tokens with another subject confirmation method than bearer. The attacker could then use such a token to create a log in session. Saml2 tokens are usually used as bearer tokens - a caller that presents a token is assumed to be the subject of the token. There is also support in the Saml2 protocol for issuing tokens that is tied to a subject through other means, e.g. holder-of-key where possession of a private key must be proved.

The issue concerns a faulty implementation of Token Replay Detection, an important defense measure for Single Sign On solutions. This faulty implementation affects the specified versions of the Sustainsys.Saml2 NuGet package for ASP.NET. Token Replay Detection is crucial for preventing replay attacks, where an attacker intercepts and reuses a valid token to gain unauthorized access. The correct implementation of Token Replay Detection is essential for the security of Single Sign On solutions.