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CoreWCF.Primitives SAML 1.1 token validation bypass

Security advisory: SAML 1.1 token validation bypass in CoreWCF.Primitives. Two exploit shapes: holder-of-key downgrade (attacker can present a holder-of-key ass

20 Jun 2026Read 1 minSeverity: act now

What changed

Security advisory: SAML 1.1 token validation bypass in CoreWCF.Primitives. Two exploit shapes: holder-of-key downgrade (attacker can present a holder-of-key assertion without proof key) and custom-method bypass (attacker can use a non-standard confirmation method URI).

Who it affects

Services configured to accept SAML 1.1 tokens via federation (e.g., WS2007FederationHttpBinding, WSFederationHttpBinding, or custom bindings with IssuedSecurityTokenParameters and SAML 1.1 token type).

What to do today

Upgrade CoreWCF to v1.8.1 or v1.9.1 immediately.

The trail
Collected Audited Written Published