What’s Vulnerable › Vulnerabilities

CVE-2026-54781: CoreWCF: SAML SubjectConfirmation methods and holder-of-key proof keys are not enforced

• Severity: high (CVSS 7.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-08 · updated 2026-07-09
• Weakness: CWE-287

Description

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.

Affected products

• CoreWCF: from 1.9.0, < 1.9.1; before 1.8.1

References

• 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/security/advisories/GHSA-48pq-2xq3-c2m4

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