CVE-2026-54774 CoreWCF: SamlSerializer skips SignatureValue verification when SAML signing token is not an X.509 certificate
Attackers can bypass SAML assertion signature verification in CoreWCF services by using non-X.509 signing tokens, undermining authentication integrity.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-54774?
CVE-2026-54774 is a high-severity 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, SamlSerializer skips final SignatureValue verification when a CoreWCF service validates SAML tokens using a non-X.509 signing token, allowing an attacker to reference a non-X.509 SecurityToken key identifier and bypass assertion signature verification. This issue is fixed in versions 1.8.1 and 1.9.1.
Which versions are affected by CVE-2026-54774?
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-2026-54774?
Upgrade CoreWCF.Primitives to a fixed version for your release line: 1.8.1 or 1.9.1.
Is CVE-2026-54774 being exploited?
There is no known exploitation of CVE-2026-54774 in the wild and no public exploit code.
Sources
Also known as GHSA-rpj7-hr7h-w6p9.