# CVE-2026-54781: CoreWCF improper authentication in SAML SamlSecurityTokenHandler

Source: https://junglewise.ai/threats/cve-2026-54781-corewcf-improper-authentication-in-saml-samlsecuritytokenhandler  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-08. Updated: 2026-07-08  
License: CC BY 4.0 with a link back

CVE-2026-54781 · Severity: high · CVSS 7.4 · Published 2026-07-08

CoreWCF, a library used to build web services in .NET, contains a security flaw in how it validates identity tokens. An attacker could bypass security checks by providing a specially crafted identity assertion that the system incorrectly trusts without proper proof. This could allow an unauthorized user to impersonate a legitimate user and gain access to protected data or operations.

Technologies: [CoreWCF](https://junglewise.ai/threats/technologies/corewcf), [CoreWCF.Primitives (NuGet)](https://junglewise.ai/threats/technologies/corewcf-primitives). Vendors: [CoreWCF](https://junglewise.ai/threats/vendors/corewcf), [NuGet](https://junglewise.ai/threats/vendors/nuget).

## Quick answers

**Is CVE-2026-54781 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-54781 being exploited in the wild.

**How severe is CVE-2026-54781?** High severity, with a CVSS score of 7.4, 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-2026-54781?** 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-2026-54781 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-54781?** 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

  ```sh
  dotnet add package CoreWCF.Primitives --version 1.8.1
  ```


## Technical details

A vulnerability exists in CoreWCF's SamlSecurityTokenHandler where SubjectConfirmationMethod URIs and holder-of-key proof keys are not strictly enforced. Specifically, the handler does not verify that incoming assertions belong to the SAML 1.1 defined set, nor does it require the <SubjectConfirmation><KeyInfo> element for holder-of-key assertions. An attacker can exploit this by providing an assertion with a fabricated confirmation method or no proof key, which the system treats as a bearer token. This allows the attacker to authenticate as a subject without proving authority over the assertion. The issue is resolved in versions 1.8.1 and 1.9.1 by validating that methods are restricted to the SAML 1.1 trio (bearer, sender-vouches, holder-of-key) and ensuring holder-of-key subjects carry a valid KeyInfo.

## Affected products

- CoreWCF CoreWCF < 1.8.1, >= 1.9.0 < 1.9.1

## Identifiers

- CVE-2026-54781
- GHSA-48pq-2xq3-c2m4

## Timeline

- 2026-06-16: patched: Fixed in versions 1.8.1 and 1.9.1
- 2026-07-08: advisory: NVD publication date

## References

- [https://github.com/CoreWCF/CoreWCF/commit/6a99df3242f54acd6f89edfd6050430b72d0c685](https://github.com/CoreWCF/CoreWCF/commit/6a99df3242f54acd6f89edfd6050430b72d0c685)
- [https://github.com/CoreWCF/CoreWCF/commit/86dd3232b6b8aaf32281be9e8d798afad6145d58](https://github.com/CoreWCF/CoreWCF/commit/86dd3232b6b8aaf32281be9e8d798afad6145d58)
- [https://github.com/CoreWCF/CoreWCF/commit/9eb9b46d1c2af06fb71f656a02f4d5b4649c1f03](https://github.com/CoreWCF/CoreWCF/commit/9eb9b46d1c2af06fb71f656a02f4d5b4649c1f03)
- [https://github.com/CoreWCF/CoreWCF/releases/tag/v1.8.1](https://github.com/CoreWCF/CoreWCF/releases/tag/v1.8.1)
- [https://github.com/CoreWCF/CoreWCF/releases/tag/v1.9.1](https://github.com/CoreWCF/CoreWCF/releases/tag/v1.9.1)
- [https://github.com/CoreWCF/CoreWCF/security/advisories/GHSA-48pq-2xq3-c2m4](https://github.com/CoreWCF/CoreWCF/security/advisories/GHSA-48pq-2xq3-c2m4)

## Related threats

- [CoreWCF cleartext proof key exposure in SPNEGO negotiation](https://junglewise.ai/threats/cve-2026-54784-corewcf-cleartext-proof-key-exposure-in-spnego-negotiation)
- [CoreWCF signature verification bypass in WS-Security](https://junglewise.ai/threats/cve-2026-54783-corewcf-signature-verification-bypass-in-ws-security)
- [CoreWCF authentication bypass in SAML token validation](https://junglewise.ai/threats/cve-2026-54782-corewcf-authentication-bypass-in-saml-token-validation)
- [CoreWCF algorithm downgrade in WS-Security receive pipeline](https://junglewise.ai/threats/cve-2026-54780-corewcf-algorithm-downgrade-in-ws-security-receive-pipeline)
- [CoreWCF SAML token replay protection bypass in DefaultTokenReplayCache](https://junglewise.ai/threats/cve-2026-54779-corewcf-saml-token-replay-protection-bypass-in)