CVE-2026-54782
CoreWCF: Authentication bypass in CoreWCF SAML 1.1 / 2.0 token signature validation
CoreWCF is a port of the service side of Windows Communication Foundation (WCF) to .NET Core. Prior to 1.8.1 and 1.9.1, CoreWCF SAML 1.1 and SAML 2.0 token validation does not correctly resolve the issuer signing key or require signed tokens when IdentityConfiguration is used with federated bindings, allowing an unauthenticated remote attacker to impersonate any principal the trusted STS could issue. This issue is fixed in versions 1.8.1 and 1.9.1.
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
- High
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
CoreWCF: Authentication bypass in CoreWCF SAML 1.1 / 2.0 token signature validation
CoreWCF is a port of the service side of Windows Communication Foundation (WCF) to .NET Core. Prior to 1.8.1 and 1.9.1, CoreWCF SAML 1.1 and SAML 2.0 token validation does not correctly resolve the issuer signing key or require signed tokens when IdentityConfiguration is used with federated bindings, allowing an unauthenticated remote attacker to impersonate any principal the trusted STS could issue. This issue is fixed in versions 1.8.1 and 1.9.1.
- Record
CVE-2026-54782- CVSS 3.1
- 10.0 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N - Weakness
- CWE-290, CWE-347
- Updated
- 2026-11-02
EUVDEUVD-2026-42473
CoreWCF is a port of the service side of Windows Communication Foundation (WCF) to .NET Core. Prior to 1.8.1 and 1.9.1, CoreWCF SAML 1.1 and SAML 2.0 token validation does not correctly resolve the issuer signing key or require signed tokens when IdentityConfiguration is used with federated bindings, allowing an unauthenticated remote attacker to impersonate any principal the trusted STS could issue. This issue is fixed in versions 1.8.1 and 1.9.1.
- Record
EUVD-2026-42473- CVSS 3.1
- 10.0 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-xjr9-gg9q-jx3v
CoreWCF: Authentication bypass in CoreWCF SAML 1.1 / 2.0 token signature validation
Impact
Full impersonation of any principal the trusted STS could have issued an assertion for — including administrative principals when the relying party grants them via SAML claims. Affects both SAML 1.1 and SAML 2.0.
Preconditions
Relying-party service is hosted with WSFederationHttpBinding or WS2007FederationHttpBinding (or any binding that triggers FederatedSecurityTokenManager for issued-token validation), and IdentityConfiguration is wired (UseIdentityConfiguration = true). Attacker can reach the service over the network and knows the trusted STS’s public certificate (public certs are by design discoverable).
Patches
Fixed in CoreWCF v1.8.1 and v1.9.1
Workarounds
None
- Record
GHSA-xjr9-gg9q-jx3v- CVSS 3.1
- 10.0 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N - Weakness
- CWE-290, CWE-347
- Updated
- 2026-11-02
NVD
CoreWCF is a port of the service side of Windows Communication Foundation (WCF) to .NET Core. Prior to 1.8.1 and 1.9.1, CoreWCF SAML 1.1 and SAML 2.0 token validation does not correctly resolve the issuer signing key or require signed tokens when IdentityConfiguration is used with federated bindings, allowing an unauthenticated remote attacker to impersonate any principal the trusted STS could issue. This issue is fixed in versions 1.8.1 and 1.9.1.
- Record
CVE-2026-54782- CVSS 3.1
- 10.0 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N - Weakness
- CWE-290, CWE-347
- Updated
- 2026-11-02
OSV
CoreWCF: Authentication bypass in CoreWCF SAML 1.1 / 2.0 token signature validation
CoreWCF is a port of the service side of Windows Communication Foundation (WCF) to .NET Core. Prior to 1.8.1 and 1.9.1, CoreWCF SAML 1.1 and SAML 2.0 token validation does not correctly resolve the issuer signing key or require signed tokens when IdentityConfiguration is used with federated bindings, allowing an unauthenticated remote attacker to impersonate any principal the trusted STS could issue. This issue is fixed in versions 1.8.1 and 1.9.1.
- Record
CVE-2026-54782- CVSS 3.1
- 10.0 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N - Weakness
- CWE-290, CWE-347
- Updated
- 2026-11-02
OSVGHSA-xjr9-gg9q-jx3v
CoreWCF: Authentication bypass in CoreWCF SAML 1.1 / 2.0 token signature validation
Impact
Full impersonation of any principal the trusted STS could have issued an assertion for — including administrative principals when the relying party grants them via SAML claims. Affects both SAML 1.1 and SAML 2.0.
Preconditions
Relying-party service is hosted with WSFederationHttpBinding or WS2007FederationHttpBinding (or any binding that triggers FederatedSecurityTokenManager for issued-token validation), and IdentityConfiguration is wired (UseIdentityConfiguration = true). Attacker can reach the service over the network and knows the trusted STS’s public certificate (public certs are by design discoverable).
Patches
Fixed in CoreWCF v1.8.1 and v1.9.1
Workarounds
None
- Record
GHSA-xjr9-gg9q-jx3v- CVSS 3.1
- 10.0 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N - Weakness
- CWE-290, CWE-347
- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
CoreWCF.PrimitivesNuGet |
before 1.8.1 | 1.8.1 |
CoreWCF.PrimitivesNuGet |
1.9.0 up to 1.9.1 | 1.9.1 |
CoreWCF.PrimitivesNuGet |
before 1.8.1, plus listed versions 0.1.00.1.0-preview0.1.0-preview-20.2.00.2.1 Show 27 moreShow less0.3.00.3.10.3.20.4.01.0.01.0.0-preview11.0.0-preview21.0.11.0.21.1.01.1.11.2.01.2.11.3.01.3.11.3.21.4.01.4.0-preview11.4.11.4.21.5.01.5.0-preview11.5.11.5.21.6.01.7.01.8.0 |
1.8.1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-54782 is a critical vulnerability (CVSS 10.0) in Corewcf, published June 19, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.41%, the 35th percentile. Fixed in CoreWCF.Primitives 1.8.1.
References
github.com/CoreWCF/CoreWCF/security/advisories/GHSA-xjr9-gg9q-jx3v