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CVE-2026-54781: 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 SubjectConfir

highCVSS 7.4CVE-2026-54781
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.

Details

Source
NVD Recent CVEs (US · database · site)
Severity
high — CVSS 7.4
Published
2026-07-08
Last updated
2026-07-09
Exploitation
Not in CISA KEV at last sync

Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-54781

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Referenced CVEs

CVECSIRTS overviewExternal
CVE-2026-54781coverage & exploitation statusNVD · CVE.org

Recent advisories for CoreWCF is a

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

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