CVE-2023-41890
Sustainsys.Saml2 Insufficient Identity Provider Issuer Validation
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Sustainsys.Saml2 Insufficient Identity Provider Issuer Validation
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.
- Record
CVE-2023-41890- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Weakness
- CWE-289, CWE-294
- Updated
- 2026-11-02
EUVDEUVD-2023-2496
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.
- Record
EUVD-2023-2496- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-fv2h-753j-9g39
Sustainsys.Saml2 Insufficient Identity Provider Issuer Validation
Impact
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
- items in the stored request state (AuthenticationProperties)
Patches
Patched in version 2.9.2 and 1.0.3. All previous versions are vulnerable.
Workarounds
The AcsCommandResultCreated notification can be used to add the validation required if an upgrade to patched packages is not possible.
References
The patch is linked to https://github.com/Sustainsys/Saml2/issues/712 and https://github.com/Sustainsys/Saml2/issues/713
- Record
GHSA-fv2h-753j-9g39- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Weakness
- CWE-289, CWE-294
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2023-41890- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Weakness
- CWE-289, CWE-294
- Updated
- 2026-11-02
OSV
Sustainsys.Saml2 Insufficient Identity Provider Issuer Validation
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.
- Record
CVE-2023-41890- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Weakness
- CWE-289, CWE-294
- Updated
- 2026-11-02
OSVGHSA-fv2h-753j-9g39
Sustainsys.Saml2 Insufficient Identity Provider Issuer Validation
Impact
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
- items in the stored request state (AuthenticationProperties)
Patches
Patched in version 2.9.2 and 1.0.3. All previous versions are vulnerable.
Workarounds
The AcsCommandResultCreated notification can be used to add the validation required if an upgrade to patched packages is not possible.
References
The patch is linked to https://github.com/Sustainsys/Saml2/issues/712 and https://github.com/Sustainsys/Saml2/issues/713
- Record
GHSA-fv2h-753j-9g39- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Weakness
- CWE-289, CWE-294
- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
Sustainsys.Saml2NuGet |
before 1.0.3 | 1.0.3 |
Sustainsys.Saml2NuGet |
2.0.0 up to 2.9.2 | 2.9.2 |
Kentor.AuthServicesNuGet |
through 0.23.0 | None known |
Sustainsys.Saml2NuGet |
before 1.0.3, plus listed versions 0.23.00.24.01.0.01.0.11.0.2 |
1.0.3 |
Sustainsys.Saml2NuGet |
2.0.0 up to 2.9.2, plus listed versions 2.1.02.2.02.3.02.4.02.5.0 Show 5 moreShow less2.6.02.7.02.8.02.9.02.9.1 |
2.9.2 |
Kentor.AuthServicesNuGet |
through 0.23.0, plus listed versions 0.1.00.10.00.11.00.12.00.13.0 Show 26 moreShow less0.14.00.15.00.15.10.16.00.17.00.17.10.17.20.18.00.18.10.19.00.2.00.20.00.21.00.21.10.21.20.22.00.3.00.4.00.5.00.5.20.6.00.6.20.7.00.7.20.8.00.9.0 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases, products, published | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2023-41890 is a high vulnerability (CVSS 7.5) in Simplesamlphp Saml2, published September 19, 2023. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.75%, the 55th percentile. Fixed in Sustainsys.Saml2 1.0.3.
References
github.com/Sustainsys/Saml2/security/advisories/GHSA-fv2h-753j-9g39
nvd.nist.gov/vuln/detail/CVE-2023-41890