CVE-2026-54782: CoreWCF authentication bypass in SAML token validation

CVE-2026-54782 · Severity: critical · CVSS 10 · Published 2026-07-08

CoreWCF is a modern version of a Microsoft framework used by developers to build networked applications. A security flaw in how it handles login tokens (SAML) allows an attacker to bypass security checks and pretend to be any user. This could lead to unauthorized access to sensitive data or administrative functions without needing a valid password or signature.

Technologies: CoreWCF, CoreWCF.Primitives (NuGet). Vendors: CoreWCF, NuGet.

Quick answers

Is CVE-2026-54782 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-54782 being exploited in the wild.
How severe is CVE-2026-54782?
Critical severity, with a CVSS score of 10, published 8 July 2026.
Which products and versions are affected?
CoreWCF < 1.8.1, >= 1.9.0 < 1.9.1; CoreWCF.Primitives (NuGet) ECOSYSTEM:introduced=0,fixed=1.8.1.
Is there a fix for CVE-2026-54782?
Yes. CoreWCF.Primitives (NuGet): upgrade to 1.8.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-54782 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-54782?
Check whether you run CoreWCF or CoreWCF.Primitives (NuGet) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • CoreWCF.Primitives (NuGet): upgrade to 1.8.1 or later
    dotnet add package CoreWCF.Primitives --version 1.8.1

Technical details

A vulnerability exists in CoreWCF's SAML 1.1 and SAML 2.0 token validation logic when using IdentityConfiguration with federated bindings. The root cause is a failure to correctly resolve the issuer signing key and a lack of enforcement for signed tokens. An unauthenticated remote attacker can exploit this by providing an unsigned or improperly signed token to impersonate any user or principal that the trusted Security Token Service (STS) is authorized to issue. This is classified as an authentication bypass by spoofing (CWE-290) and improper verification of cryptographic signatures (CWE-347). The issue is resolved in versions 1.8.1 and 1.9.1 by requiring signed tokens and implementing a proper IssuerSigningKeyResolver.

Affected products

  • CoreWCF CoreWCF < 1.8.1, >= 1.9.0 < 1.9.1

Identifiers

  • CVE-2026-54782
  • GHSA-xjr9-gg9q-jx3v

Timeline

  • 2026-07-08: disclosed
  • 2026-07-08: advisory

References

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