CoreWCF: SAML SubjectConfirmation methods and holder-of-key proof keys are not enforced
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- High
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- High · High · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-287.
Summary
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 token validation does not enforce SubjectConfirmation method URIs or holder-of-key proof keys in SamlSecurityTokenHandler, allowing holder-of-key downgrade or custom confirmation method assertions to authenticate a subject without proving authority over the assertion. This issue is fixed in versions 1.8.1 and 1.9.1.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| CoreWCF | CoreWCF | 1.9.0 to before 1.9.1; before 1.8.1 | 1.9.1, 1.8.1 | Patch available | CNA |
| — | CoreWCF.Primitives (NuGet) | before 1.8.1 | 1.8.1 | Patch available | GHSA-48pq-2xq3-c2m4 |
| — | CoreWCF.Primitives (NuGet) | 1.9.0 to before 1.9.1 | 1.9.1 | Patch available | GHSA-48pq-2xq3-c2m4 |
- CoreWCF VendorCoreWCF Affected 1.9.0 to before 1.9.1; before 1.8.1 Fixed in 1.9.1, 1.8.1 Patch available CNA
- CoreWCF.Primitives (NuGet) Vendor— Affected before 1.8.1 Fixed in 1.8.1 Patch available GHSA-48pq-2xq3-c2m4
- CoreWCF.Primitives (NuGet) Vendor— Affected 1.9.0 to before 1.9.1 Fixed in 1.9.1 Patch available GHSA-48pq-2xq3-c2m4
Remediation
- Fix · CNA CoreWCF (CoreWCF) Fixed in 1.9.1, 1.8.1
- Fix · GHSA-48pq-2xq3-c2m4 CoreWCF.Primitives (NuGet) Fixed in 1.8.1 Advisory →
- Fix · GHSA-48pq-2xq3-c2m4 CoreWCF.Primitives (NuGet) Fixed in 1.9.1 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-54781
- 2026-10-03 Alias added: GHSA-48pq-2xq3-c2m4
References
Other 7
- https://github.com/CoreWCF/CoreWCF/security/advisories/GHSA-48pq-2xq3-c2m4
- https://github.com/CoreWCF/CoreWCF/commit/6a99df3242f54acd6f89edfd6050430b72d0c685
- https://github.com/CoreWCF/CoreWCF/commit/86dd3232b6b8aaf32281be9e8d798afad6145d58
- https://github.com/CoreWCF/CoreWCF/commit/9eb9b46d1c2af06fb71f656a02f4d5b4649c1f03
- https://github.com/CoreWCF/CoreWCF/releases/tag/v1.8.1
- https://github.com/CoreWCF/CoreWCF/releases/tag/v1.9.1
- https://github.com/CoreWCF/CoreWCF
More CoreWCF vulnerabilities
- TI-2026-39588 CoreWCF: Authentication bypass in CoreWCF SAML 1.1 / 2.0 token signature validation CVSS 3.1CRITICAL 10.0
- TI-2026-39578 CoreWCF: Pre-authentication infinite-loop CPU exhaustion in CoreWCF net.tcp / net.pipe / net.uds framing handshake CVSS 3.1HIGH 7.5
- TI-2024-18811 CoreWCF NetFraming based services can leave connections open when they should be closed CVSS 3.1HIGH 7.5
- TI-2026-39590 CoreWCF: SPNEGO SecurityContextToken proof key wrapped without confidentiality CVSS 3.1HIGH 7.4
- TI-2026-39589 Authentication bypass by capture-replay in CoreWCF CVSS 3.1HIGH 7.4
- TI-2026-39580 CoreWCF: SamlSerializer skips SignatureValue verification when SAML signing token is not an X.509 certificate CVSS 3.1HIGH 7.4
Sources
- CVE-2026-54781 · CVE Program
- CVE-2026-54781 · NVD
- FIRST EPSS
- GHSA-48pq-2xq3-c2m4 · GitHub Advisory Database · CC BY 4.0
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