Sustainsys · Sustainsys.Saml2 · CVE-2023-41890
**Name of the Vulnerable Software and Affected Versions**
Sustainsys.Saml2 versions prior to 1.0.3
Sustainsys.Saml2 versions prior to 2.9.2
**Description**
The Sustainsys.Saml2 library adds SAML2P support to ASP.NET web sites, allowing the web site to act as a SAML2 Service Provider. When a response is processed, the issuer of the Identity Provider is not sufficiently validated. This could allow a malicious identity provider to craft a Saml2 response that is processed as if issued by another identity provider. It is also possible for a malicious end user to cause stored state intended for one identity provider to be used when processing the response from another provider. An application is impacted if they rely on any of these features in their authentication/authorization logic: the issuer of the generated identity and claims; or items in the stored request state (AuthenticationProperties).
**Recommendations**
For versions prior to 1.0.3, update to version 1.0.3 or later.
For versions prior to 2.9.2, update to version 2.9.2 or later.
As a temporary workaround, consider using the `AcsCommandResultCreated` notification to add the validation required if an upgrade to patched packages is not possible.