CVE-2026-54782 CoreWCF: Authentication bypass in CoreWCF SAML 1.1 / 2.0 token signature validation
An unauthenticated attacker can impersonate any principal in CoreWCF applications using federated bindings due to flawed SAML token signature validation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-54782?
CVE-2026-54782 is a critical authentication bypass vulnerability in CoreWCF, published on 8 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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 1.1 and SAML 2.0 token validation does not correctly resolve the issuer signing key or require signed tokens when IdentityConfiguration is used with federated bindings, allowing an unauthenticated remote attacker to impersonate any principal the trusted STS could issue. This issue is fixed in versions 1.8.1 and 1.9.1.
Which versions are affected by CVE-2026-54782?
4 open source packages ship an affected version, including CoreWCF.Primitives.
| Package | Affected | Fixed in |
|---|---|---|
CoreWCF.Primitives NuGet | All versions | 1.8.1 |
CoreWCF.Primitives NuGet | All versions | 1.8.1 |
CoreWCF.Primitives NuGet | From 1.9.0 | 1.9.1 |
CoreWCF.Primitives NuGet | From 1.9.0 | 1.9.1 |
How do I fix CVE-2026-54782?
Upgrade CoreWCF.Primitives to a fixed version for your release line: 1.8.1 or 1.9.1.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-54782 being exploited?
There is no known exploitation of CVE-2026-54782 in the wild and no public exploit code.
Sources
Also known as GHSA-xjr9-gg9q-jx3v.