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Vulnerability · Published Jul 8, 2026 · Assigned by GitHub_M

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

High 7.4

In plain English

A high-severity improper authentication in CoreWCF from CoreWCF. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 16% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.4High
Exploit odds (30 days)0.2%top 83.8% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

EcosystemPackageFixed inAdvisory
NuGetcorewcf.primitives1.8.1GHSA-48pq-2xq3-c2m4
NuGetcorewcf.primitives1.9.1GHSA-48pq-2xq3-c2m4

Affected products (as reported)

VendorProductVersions
CoreWCF CoreWCF >= 1.9.0, < 1.9.1< 1.8.1

Weakness: CWE-287, CWE-345 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

References